I tried to build the source tarball on Mac OS X 10.5.8. I used GHC 7.6.1, which I also built myself (without any problem) and installed in /Library/Frameworks/GHC.framework/Versions/7.6.1/usr. I got this:
HC [stage 0] ghc/stage1/build/hschooks.o
ghc/hschooks.c:36:0:
error: conflicting types for ‘StackOverflowHook’
/Library/Frameworks/GHC.framework/Versions/7.6.1/usr/lib/ghc-7.6.1/include/rts/Hooks.h:21:0:
error: previous declaration of ‘StackOverflowHook’ was here
make[1]: *** [ghc/stage1/build/hschooks.o] Error 1
make: *** [all] Error 2