I can do both 32 and 64-bit builds.I started with 32 bits.
I got
"inplace/bin/ghc-stage2.exe" -hisuf hi -osuf o -hcsuf hc -static -H64m -O0 -fasm -package-name vector -0.10.9.1 -hide-all-packages -i -ilibraries/vector/. -ilibraries/vector/dist-install/build -ilibraries/vec tor/dist-install/build/autogen -Ilibraries/vector/dist-install/build -Ilibraries/vector/dist-install/build /autogen -Ilibraries/vector/include -Ilibraries/vector/internal -optP-DVECTOR_BOUNDS_CHECKS -optP-includ e -optPlibraries/vector/dist-install/build/autogen/cabal_macros.h -package base-4.7.1.0 -package deepseq-1 .3.0.2 -package ghc-prim-0.3.1.0 -package primitive-0.5.2.1 -O2 -XHaskell98 -XCPP -XDeriveDataTypeable -O -fasm -no-user-package-db -rtsopts -odir libraries/vector/dist-install/build -hidir libraries/vector /dist-install/build -stubdir libraries/vector/dist-install/build -c libraries/vector/./Data/Vector/Fusio n/Stream/Monadic.hs -o libraries/vector/dist-install/build/Data/Vector/Fusion/Stream/Monadic.o
"/usr/bin/ar" q libraries/primitive/dist-install/build/libHSprimitive-0.5.2.1.a @libraries/primitive/dist -install/build/libHSprimitive-0.5.2.1.a.contents
/usr/bin/ar: creating libraries/primitive/dist-install/build/libHSprimitive-0.5.2.1.a
"rm" -f libraries/primitive/dist-install/build/libHSprimitive-0.5.2.1.a.contents
Loading package ghc-prim ... linking ... done.
Loading package integer-gmp2 ... linking ... ghc-stage2.exe: unable to load package `integer-gmp2'
ghc-stage2.exe: D:\Niklas\scratch\ghc-build\msys\home\niklas\ghc\libraries\integer-gmp2\dist-install\build \HSinteger-gmp2-0.0.1.0.o: unknown symbol `_scalbn'
I built it´with gmp-6.0.0.