IntrospectionTest mostly does nothing when built by Clang

[pogo59]

As a side project, I'm working on gtest features to detect unittests that have assertions that aren't executed. When I use gcc as my build compiler, IntrospectionTest builds and runs fine. However, when I use clang as my build compiler, IntrospectionTest builds but skips most of its tests; it appears that NodeIntrospection::hasIntrospectionSupport() returns false.

I've verified that my cmake commands for both build trees are the same, and I see that CLANG_TOOLING_BUILD_AST_INTROSPECTION is ON in CMakeCache.txt. I don't understand why it's taking the "off" path in this case, and failing to generate the fully functional header.

If this is some subtle misconfiguration error on my part, great; if not, it seems like the conditions in the Introspection/CMakeLists.txt needs a bit of tweaking.

[llvmbot]

@llvm/issue-subscribers-clang-frontend

[pogo59]

@steveire looks like the primary contributor of IntrospectionTest.

[pogo59]

I replaced the "return" after the "hasIntrospectionSupport()" with GTEST_SKIP in 0d54457 so the lack of support gets reported correctly as a SKIPPED test; but the question remains, why isn't it supported when I build with clang?

[steveire]

I wasn't able to make the CI tests pass on all platforms when this was submitted. I don't have the required access to the failing machines in order to determine what was wrong, so I had to disable the platforms entirely.

Feel free to re-enable them if you are able to make CI pass.