The value of the environnment variable LDFLAGS is not used to compile hug's packages. Consequently, make fails to build X11 package (on OS X 10.4.8) ; here is the make output :
Preprocessing library X11-1.2...
../../libraries/tools/hsc2hs -DHUGS -Iinclude -I/usr/X11R6/include --lflag=-lX11 -o Graphics/X11/Types.hs Graphics/X11/Types.hsc
/usr/bin/ld: can't locate file for: -lX11
collect2: ld returned 1 exit status
linking Graphics/X11/Types_hsc_make.o failed
command was: /usr/bin/gcc -lX11 Graphics/X11/Types_hsc_make.o -o Graphics/X11/Types_hsc_make
../../packages/Cabal/examples/hapax.hs: got error code while preprocessing: Graphics.X11.Types
Skipping X11 package
My LDFLAGS variable whose value is "-L/usr/X11R6/lib -L/Users/julien/local/lib" has not been used. Simply add -L/usr/X11R6/lib to the gcc command and it compile fine.
Another work around is to create a symbolic link :
sudo ln -s /usr/X11R6/lib/libX11.a /usr/lib/libX11.a