clang-cl: Expose --version.

This is for consistency with lld-link, see https://reviews.llvm.org/D38972
Also give --version a help text so it shows up in --help / /? output (for
both clang-cl and regular clang).

llvm-svn: 316335
diff --git a/clang/test/Driver/cl-options.c b/clang/test/Driver/cl-options.c
index 115b219..2435ba2 100644
--- a/clang/test/Driver/cl-options.c
+++ b/clang/test/Driver/cl-options.c
@@ -574,6 +574,7 @@
 // RUN:     -fstandalone-debug \
 // RUN:     -flimit-debug-info \
 // RUN:     -flto \
+// RUN:     --version \
 // RUN:     -Werror /Zs -- %s 2>&1