Configure Open MPI shmem defaults on macOS #4944

Job	Run time
ci-scope	4s
pre-commit / pre-commit	2m 1s
pre-commit / link-check	12s
mac / clang-build (Release)	2m 13s
mac / clang-build (Debug)	1m 56s
ubuntu / gcc-build (ubuntu-24.04, Release)	2m 19s
ubuntu / clang-build (ubuntu-24.04)	2m 44s
ubuntu / gcc-build (ubuntu-24.04, Debug)	1m 58s
windows / clang-build	2m 32s
windows / msvc-build (Debug)	2m 48s
windows / msvc-build (Release)	4m 8s
mac / clang-test	1m 46s
ubuntu / gcc-test (ubuntu-24.04)	2m 40s
windows / clang-test	1m 53s
ubuntu / clang-test (ubuntu-24.04)	2m 45s
ubuntu / clang-sanitizer-build (ubuntu-24.04)	2m 54s
mac / clang-test-extended	1m 24s
windows / msvc-test	1m 59s
windows / clang-test-extended	1m 47s
ubuntu / gcc-test-extended (ubuntu-24.04)	1m 42s
ubuntu / clang-test-extended (ubuntu-24.04)	1m 53s
ubuntu / clang-sanitizer-test (ubuntu-24.04)	1m 7s
windows / msvc-test-extended	1m 28s
ubuntu / clang-sanitizer-test-extended (ubuntu-24.04)	1m 9s
ubuntu / gcc-build-codecov	4m 7s
perf / ubuntu-gcc-build-perf-stats	1m 13s
perf / macos-clang-build-perf-stats	1m 25s
pages / build-doxygen-xml	23s
pages / build-scoreboard	19s
pages / build-sphinx	18s
pages / deploy-pages	1s
	55m 8s

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