Port r198088 (set NO_DEAD_STRIP for clang) from make to cmake.

Also stop setting passing -dead_strip explicitly for libclang and instead
rely on this now happening by default. (And make it happen by default for
add_clang_library, which doesn't use the library cmake functions from llvm.)

llvm-svn: 198200
GitOrigin-RevId: 194c00935263e88e3222a531ba1f3f2570b06eb3
3 files changed