[CMake][LLVM] Remove duplicated library mask. Broken clang linking against clangShared

Summary:
The `LLVM${c}Info` mask is listed twice in LLVM-Config.cmake. This results in the libraries such as LLVMARMInfo, LLVMAArch4Info, etc appearing twice in `extract_symbols.py` command line while building `clangShared`. `Extract_symbols.py` does not work well in such a case and completely ignores the symbols from the duplicated libraries. Thus, the LLVM(...)Info symbols do not get exported from `clangShared` and linking clang against it fails with unresolved dependencies.

Seems to be a mere copy-paste mistake.

Reviewers: beanz, chapuni

Reviewed By: chapuni

Subscribers: chapuni, aemerson, mgorny, kristof.beyls, llvm-commits, asl

Differential Revision: https://reviews.llvm.org/D36119

llvm-svn: 310590