[clang] [NFC][clang][Driver] Add tests for --driver-mode=flang (PR #207658)

[Yusuke MINATO via cfe-commits]

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@@ -0,0 +1,8 @@
+! Check that Flang runtimes are passed to the linker in --driver-mode=flang.
+
+! RUN: %clang --driver-mode=flang --rtlib=compiler-rt -### %s 2>&1 | FileCheck %s
+! CHECK-DAG: clang_rt.{{[^ "]}}
+! CHECK-DAG: flang_rt.{{[^ "]}}
+
+! RUN: not %clang --driver-mode=flang -stdlib=libc++ -### %s 2>&1 | FileCheck --check-prefix=LIBCXX %s
+! LIBCXX: clang: error: unknown argument: '-stdlib=libc++'
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yus3710-fj wrote:

Thank you for pointing that out. I have fixed it.

https://github.com/llvm/llvm-project/pull/207658