check the linker support of `--version-script` and `--exclude-libs`
flags. and use them only if they are supported.
llvm-ld does not support `--version-script` at this moment. and it's
reported that old versions of llvm-ld do not support `--exclude-libs`
as well.
Signed-off-by: Kefu Chai <kchai@redhat.com>
