clang-wpa link failure.

It appears that the build for clang-wpa is out of date and will not
link correctly with the current makefile.

I was able to get it to link with a second mention of clangSema.a
though there might be a library reordering that avoid the double
mention.

Here's the diff: (the CMakeLists might need updating as well)

llvm/tools/clang/examples/wpa$ svn diff

Index: Makefile