[runtimes] Check if pragma comment(lib, ...) is supported first

This fixes the issue introduced by r362048 where we always use
pragma comment(lib, ...) for dependent libraries when the compiler
is Clang, but older Clang versions don't support this pragma so
we need to check first if it's supported before using it.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@362055 91177308-0d34-0410-b5e6-96231b3b80d8
10 files changed