It's a very annoying anachronism of the DMD Windows 32-bit version that
leads to this error. You could try to build the GIT master version of
DUB. It now supports building individual dependencies separately and
that might solve the issue.

Tried it (with just gfm as dependency), but it doesn't work

C:\Test>dub
Checking dependencies in 'C:\Test'
Checking dependencies in 'C:\Test'
Generate target project (executable C:\Test project)
Generate target gfm (staticLibrary C:\Users\user\AppData\Roaming\dub\packages\gfm-master gfm)
Generate target gfm:math (staticLibrary C:\Users\user\AppData\Roaming\dub\packages\gfm-master gfm_math)
Generate target gfm:net (staticLibrary C:\Users\user\AppData\Roaming\dub\packages\gfm-master gfm_net)
Generate target gfm:core (staticLibrary C:\Users\user\AppData\Roaming\dub\packages\gfm-master gfm_core)
Generate target gfm:assimp (staticLibrary C:\Users\user\AppData\Roaming\dub\packages\gfm-master gfm_assimp)
Generate target derelict-assimp3 (staticLibrary C:\Users\user\AppData\Roaming\dub\packages\derelict-assimp3-master\lib De
relictASSIMP3)
Generate target derelict-util (staticLibrary C:\Users\user\AppData\Roaming\dub\packages\derelict-util-1.0.0\lib DerelictU
til)
Generate target gfm:freeimage (staticLibrary C:\Users\user\AppData\Roaming\dub\packages\gfm-master gfm_freeimage)
Generate target derelict-fi (staticLibrary C:\Users\user\AppData\Roaming\dub\packages\derelict-fi-master\lib DerelictFI)
Generate target gfm:image (staticLibrary C:\Users\user\AppData\Roaming\dub\packages\gfm-master gfm_image)
Generate target gfm:opengl (staticLibrary C:\Users\user\AppData\Roaming\dub\packages\gfm-master gfm_opengl)
Generate target derelict-gl3 (staticLibrary C:\Users\user\AppData\Roaming\dub\packages\derelict-gl3-master\lib DerelictGL
3)
Generate target gfm:sdl2 (staticLibrary C:\Users\user\AppData\Roaming\dub\packages\gfm-master gfm_sdl2)
Generate target derelict-sdl2 (staticLibrary C:\Users\user\AppData\Roaming\dub\packages\derelict-sdl2-master\lib Derelict
SDL2)
Building gfm:math configuration "library", build type debug.
Running dmd...
Building gfm:net configuration "library", build type debug.
Running dmd...
Building gfm:core configuration "library", build type debug.
Running dmd...
Building derelict-util configuration "library", build type debug.
Running dmd...
Building derelict-assimp3 configuration "library", build type debug.
Running dmd...
Building gfm:assimp configuration "library", build type debug.
Running dmd...
..\..\..\Users\user\AppData\Roaming\dub\packages\gfm-master\.dub\build\library-debug-x86-dmd-87DF8F8E7188900AFFE1391BD8BD
7DD1\gfm_assimp.lib: Error: multiple definition of exception: _D8derelict4util9exception12__ModuleInfoZ and exception: _
D8derelict4util9exception12__ModuleInfoZ
..\..\..\Users\user\AppData\Roaming\dub\packages\gfm-master\.dub\build\library-debug-x86-dmd-87DF8F8E7188900AFFE1391BD8BD
7DD1\gfm_assimp.lib: Error: multiple definition of exception: _D8derelict4util9exception7__arrayZ and exception: _D8dere
lict4util9exception7__arrayZ
..\..\..\Users\user\AppData\Roaming\dub\packages\gfm-master\.dub\build\library-debug-x86-dmd-87DF8F8E7188900AFFE1391BD8BD
7DD1\gfm_assimp.lib: Error: multiple definition of exception: _D8derelict4util9exception8__assertFiZv and exception: _D8
derelict4util9exception8__assertFiZv
..\..\..\Users\user\AppData\Roaming\dub\packages\gfm-master\.dub\build\library-debug-x86-dmd-87DF8F8E7188900AFFE1391BD8BD
7DD1\gfm_assimp.lib: Error: multiple definition of exception: _D8derelict4util9exception15__unittest_failFiZv and except
ion: _D8derelict4util9exception15__unittest_failFiZv
..\..\..\Users\user\AppData\Roaming\dub\packages\gfm-master\.dub\build\library-debug-x86-dmd-87DF8F8E7188900AFFE1391BD8BD
7DD1\gfm_assimp.lib: Error: multiple definition of exception: _D8derelict4util9exception17DerelictException6__initZ and
exception: _D8derelict4util9exception17DerelictException6__initZ
..\..\..\Users\user\AppData\Roaming\dub\packages\gfm-master\.dub\build\library-debug-x86-dmd-87DF8F8E7188900AFFE1391BD8BD
7DD1\gfm_assimp.lib: Error: multiple definition of exception: _D8derelict4util9exception17DerelictException7__ClassZ and
 exception: _D8derelict4util9exception17DerelictException7__ClassZ
..\..\..\Users\user\AppData\Roaming\dub\packages\gfm-master\.dub\build\library-debug-x86-dmd-87DF8F8E7188900AFFE1391BD8BD
7DD1\gfm_assimp.lib: Error: multiple definition of exception: _D8derelict4util9exception17DerelictException6__vtblZ and
exception: _D8derelict4util9exception17DerelictException6__vtblZ
..\..\..\Users\user\AppData\Roaming\dub\packages\gfm-master\.dub\build\library-debug-x86-dmd-87DF8F8E7188900AFFE1391BD8BD
7DD1\gfm_assimp.lib: Error: multiple definition of exception: _D8derelict4util9exception17DerelictException6__ctorMFAyaZ
C8derelict4util9exception17DerelictException and exception: _D8derelict4util9exception17DerelictException6__ctorMFAyaZC8
derelict4util9exception17DerelictException
..\..\..\Users\user\AppData\Roaming\dub\packages\gfm-master\.dub\build\library-debug-x86-dmd-87DF8F8E7188900AFFE1391BD8BD
7DD1\gfm_assimp.lib: Error: multiple definition of exception: _D8derelict4util9exception15FailedSharedLib6__initZ and ex
ception: _D8derelict4util9exception15FailedSharedLib6__initZ
..\..\..\Users\user\AppData\Roaming\dub\packages\gfm-master\.dub\build\library-debug-x86-dmd-87DF8F8E7188900AFFE1391BD8BD
7DD1\gfm_assimp.lib: Error: multiple definition of exception: _D8derelict4util9exception15FailedSharÚLib11__xopEqualsFKx
SÇ®║Ǽ¼Zb and exception: _D8derelict4util9exception15FailedSharÚLib11__xopEqualsFKxSÇ®║Ǽ¼Zb
..\..\..\Users\user\AppData\Roaming\dub\packages\gfm-master\.dub\build\library-debug-x86-dmd-87DF8F8E7188900AFFE1391BD8BD
7DD1\gfm_assimp.lib: Error: multiple definition of exception: _D8derelict4util9exception22SharedLibLoadException6__initZ
 and exception: _D8derelict4util9exception22SharedLibLoadException6__initZ
..\..\..\Users\user\AppData\Roaming\dub\packages\gfm-master\.dub\build\library-debug-x86-dmd-87DF8F8E7188900AFFE1391BD8BD
7DD1\gfm_assimp.lib: Error: multiple definition of exception: _D8derelict4util9exception22SharedLibLoadException7__Class
Z and exception: _D8derelict4util9exception22SharedLibLoadException7__ClassZ
..\..\..\Users\user\AppData\Roaming\dub\packages\gfm-master\.dub\build\library-debug-x86-dmd-87DF8F8E7188900AFFE1391BD8BD
7DD1\gfm_assimp.lib: Error: multiple definition of exception: _D8derelict4util9exception22SharedLibLoadException6__vtblZ
 and exception: _D8derelict4util9exception22SharedLibLoadException6__vtblZ
..\..\..\Users\user\AppData\Roaming\dub\packages\gfm-master\.dub\build\library-debug-x86-dmd-87DF8F8E7188900AFFE1391BD8BD
7DD1\gfm_assimp.lib: Error: multiple definition of exception: _D8derelict4util9exception22SharedLibLoadException8throwNe
wFxAAaxAAaZv and exception: _D8derelict4util9exception22SharedLibLoadException8throwNewFxAAaxAAaZv
..\..\..\Users\user\AppData\Roaming\dub\packages\gfm-master\.dub\build\library-debug-x86-dmd-87DF8F8E7188900AFFE1391BD8BD
7DD1\gfm_assimp.lib: Error: multiple definition of exception: _D8derelict4util9exception22SharedLibLoadException6__ctorM
FAyaZC8derelict4util9exception22SharedLibLoadException and exception: _D8derelict4util9exception22SharedLibLoadException
6__ctorMFAyaZC8derelict4util9exception22SharedLibLoadException
..\..\..\Users\user\AppData\Roaming\dub\packages\gfm-master\.dub\build\library-debug-x86-dmd-87DF8F8E7188900AFFE1391BD8BD
7DD1\gfm_assimp.lib: Error: multiple definition of exception: _D8derelict4util9exception22SharedLibLoadException6__ctorM
FAyaAyaZC8derelict4util9exception22SharedLibLoadException and exception: _D8derelict4util9exception22SharedLibLoadExcept
ion6__ctorMFAyaAyaZC8derelict4util9exception22SharedLibLoadException
..\..\..\Users\user\AppData\Roaming\dub\packages\gfm-master\.dub\build\library-debug-x86-dmd-87DF8F8E7188900AFFE1391BD8BD
7DD1\gfm_assimp.lib: Error: multiple definition of exception: _D8derelict4util9exception22SharedLibLoadException13shared
LibNameMFZAya and exception: _D8derelict4util9exception22SharedLibLoadException13sharedLibNameMFZAya
..\..\..\Users\user\AppData\Roaming\dub\packages\gfm-master\.dub\build\library-debug-x86-dmd-87DF8F8E7188900AFFE1391BD8BD
7DD1\gfm_assimp.lib: Error: multiple definition of exception: _D8derelict4util9exception19SymbolLoadException6__initZ an
d exception: _D8derelict4util9exception19SymbolLoadException6__initZ
..\..\..\Users\user\AppData\Roaming\dub\packages\gfm-master\.dub\build\library-debug-x86-dmd-87DF8F8E7188900AFFE1391BD8BD
7DD1\gfm_assimp.lib: Error: multiple definition of exception: _D8derelict4util9exception19SymbolLoadException7__ClassZ a
nd exception: _D8derelict4util9exception19SymbolLoadException7__ClassZ
..\..\..\Users\user\AppData\Roaming\dub\packages\gfm-master\.dub\build\library-debug-x86-dmd-87DF8F8E7188900AFFE1391BD8BD
7DD1\gfm_assimp.lib: Error: multiple definition of exception: _D8derelict4util9exception19SymbolLoadException6__vtblZ an
d exception: _D8derelict4util9exception19SymbolLoadException6__vtblZ
..\..\..\Users\user\AppData\Roaming\dub\packages\gfm-master\.dub\build\library-debug-x86-dmd-87DF8F8E7188900AFFE1391BD8BD
7DD1\gfm_assimp.lib: Error: multiple definition of exception: _D8derelict4util9exception19SymbolLoadException6__ctorMFAy
aZC8derelict4util9exception19SymbolLoadException and exception: _D8derelict4util9exception19SymbolLoadException6__ctorMF
AyaZC8derelict4util9exception19SymbolLoadException
FAIL ..\..\..\Users\user\AppData\Roaming\dub\packages\gfm-master\.dub\build\library-debug-x86-dmd-87DF8F8E7188900AFFE1391
BD8BD7DD1 gfm_assimp staticLibrary
Error executing command run: DMD compile run failed with exit code 1

Otherwise there is the unfortunate workaround to build with "dub
--build=plain" to disable debug information completely. Or, installing
VisualD and building 64-bit instead of 32-bit will solve the issue, as
it uses a different debug information format.

The workaround works, thanks!