Link LLDB only against libclang and libLLVM .a files to fix macOS build

The Xcode macOS build of LLDB is currently broken after
https://reviews.llvm.org/D23232 landed, see
http://lab.llvm.org:8080/green/job/lldb_build_test/20014/console,
because we’re trying to link against all .a files found in the
llvm-build/lib directory. Let’s be more specific in what we link
against. This patch applies a regexp to only use “libclang.*”,
“libLLVM.*” and not “libclang_rt.*” static archives.

Change by Kuba Mracek (formerly Kuba Brecka)

See review here:
https://reviews.llvm.org/D23444

Reviewers: tfiala, compnerd
llvm-svn: 278527