Configure Open MPI shmem defaults on macOS #4939

Job	Run time
ci-scope	6s
pre-commit / link-check	13s
pre-commit / pre-commit	2m 21s
mac / clang-build (Debug)	3m 7s
mac / clang-build (Release)	3m 3s
windows / msvc-build (Release)	3m 9s
ubuntu / clang-build (ubuntu-24.04)	3m 14s
windows / msvc-build (Debug)	4m 10s
windows / clang-build	3m 39s
ubuntu / gcc-build (ubuntu-24.04, Debug)	2m 14s
ubuntu / gcc-build (ubuntu-24.04, Release)	2m 30s
ubuntu / gcc-test (ubuntu-24.04)	2m 43s
mac / clang-test	1m 36s
ubuntu / clang-sanitizer-build (ubuntu-24.04)	3m 14s
ubuntu / clang-test (ubuntu-24.04)	2m 38s
windows / clang-test	1m 32s
windows / msvc-test	1m 57s
mac / clang-test-extended	1m 10s
windows / clang-test-extended	1m 43s
ubuntu / gcc-test-extended (ubuntu-24.04)	1m 55s
ubuntu / clang-test-extended (ubuntu-24.04)	1m 48s
windows / msvc-test-extended	1m 34s
ubuntu / clang-sanitizer-test (ubuntu-24.04)	1m 4s
ubuntu / clang-sanitizer-test-extended (ubuntu-24.04)	35s
ubuntu / gcc-build-codecov	24s
perf	-1s
pages	0s
	51m 38s

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