[HOT FIX] Stabilize macOS CI tests: OpenMP linking, MPI env, per-test isolation #4241

Job	Run time
pre-commit / pre-commit	1m 10s
ubuntu / clang-build (ubuntu-24.04-arm)	1m 58s
ubuntu / gcc-build (ubuntu-24.04, Debug)	2m 29s
ubuntu / gcc-build (ubuntu-24.04-arm, Debug)	1m 38s
ubuntu / gcc-build (ubuntu-24.04-arm, Release)	1m 57s
mac / clang-build (Debug)	2m 27s
mac / clang-build (Release)	2m 46s
ubuntu / clang-build (ubuntu-24.04)	2m 40s
windows / msvc-build (Release)	3m 51s
windows / msvc-build (Debug)	3m 26s
windows / clang-build	4m 6s
ubuntu / gcc-build (ubuntu-24.04, Release)	2m 45s
ubuntu / clang-sanitizer-build (ubuntu-24.04)	3m 38s
ubuntu / clang-test (ubuntu-24.04)	5m 57s
ubuntu / clang-test (ubuntu-24.04-arm)	5m 55s
ubuntu / gcc-test (ubuntu-24.04-arm)	5m 50s
ubuntu / gcc-test (ubuntu-24.04)	5m 55s
mac / clang-test	1m 52s
windows / msvc-test	1m 42s
windows / clang-test	2m 35s
mac / clang-test-extended	0s
windows / msvc-test-extended	-1s
ubuntu / clang-sanitizer-test (ubuntu-24.04)	2m 17s
windows / clang-test-extended	1m 59s
ubuntu / clang-sanitizer-test-extended	1s
ubuntu / clang-test-extended	1s
ubuntu / gcc-test-extended	1s
ubuntu / gcc-build-codecov	1s
perf	0s
pages	-1s
	1h 8m 55s

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