Before, we would end up with the LLVM_LIBRARIES variable containing,
for example, "-lLLVMAnalysis;-lz" and the Zig compiler CLI would be
stuck with ambiguous library names. In this branch, that ambiguity is
not allowed; it will look for a dynamically linked LLVMAnalysis and fail
to find it in the case that the build of LLVM is static.

With this change, LLVM_LIBRARIES will contain, for example,
"/full/path/to/libLLVMAnalysis.a;-lz" and it is unambiguous that the
first library should be linked statically and the second dynamically.

In the case of a dynamically linked system LLVM, it will look like
"/full/path/to/libLLVM.so;-lz" which again is fully unambiguous.

This fixes building Zig from source.