Merge pull request #17744 from mppf/skip-llvm-testing-three-extern
Use skipif/compopts to work around some LLVM issues while I investigate
For the sake of nightly testing, uses skipif/compopt to disable 3 tests with LLVM testing.
I'm planning to fix all 3 of these in PR #17409 which gets extern/unions/externUnionNoTypedef.chpl working.
Test change only - not reviewed.
Modified Files: A test/extern/ferguson/externblock/flexible-array-member.skipif