when building libobjc2 with Makefile.clang, the `llc' tool is responsible for
generating native code from the LLVM bitcodes generated by clang. So we needed
to tell llc to build relocatable code. This should be fixed in trunk, but
Makefile.clang still seems horribly out of date. But you should be able to
build the library with `CC=clang make -f Makefile' as well.