[clang] [clang][mingw] Try both native and ARM64EC triples when looking for a sysroot on the ARM64EC target (PR #210017)

[Jacek Caban via cfe-commits]

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@@ -103,3 +107,13 @@
 
 // RUN: %t.dir/testroot-custom-triple/bin/clang -no-canonical-prefixes --target=x86_64-w64-mingw32foo -rtlib=compiler-rt -stdlib=libstdc++ --sysroot="" -c -### %s 2>&1 | FileCheck -check-prefix=CHECK_TESTROOT_CUSTOM_TRIPLE %s
 // CHECK_TESTROOT_CUSTOM_TRIPLE: "{{[^"]+}}/testroot-custom-triple{{/|\\\\}}x86_64-w64-mingw32foo{{/|\\\\}}include"
+
+// Check that the arm64ec target uses the aarch64 sysroot if a separate arm64ec sysroot is not found.
+
+// RUN: %t.dir/testroot-clang/bin/aarch64-w64-mingw32-clang -no-canonical-prefixes --target=aarch64-w64-mingw32 -rtlib=compiler-rt -stdlib=libstdc++ --sysroot="" -c -### %s 2>&1 | FileCheck -check-prefix=CHECK_TESTROOT_CLANG_AARCH64 %s
+// RUN: %t.dir/testroot-clang/bin/arm64ec-w64-mingw32-clang -no-canonical-prefixes --target=arm64ec-w64-mingw32 -rtlib=compiler-rt -stdlib=libstdc++ --sysroot="" -c -### %s 2>&1 | FileCheck -check-prefix=CHECK_TESTROOT_CLANG_AARCH64 %s
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cjacek wrote:

I think we don't test it, I added such test now. Thanks.

https://github.com/llvm/llvm-project/pull/210017