Adjust detection of function multi-versioning #532

Job	Run time
coverage	7m 28s
test-cxx (ubuntu-22.04, g++, yes)	4m 34s
test-cxx (ubuntu-22.04, clang++, yes)	4m 25s
test-cxx (macos-12, clang++, no)	4m 2s
test-python (ubuntu-22.04, gcc, g++, 3.8)	3m 46s
test-python (ubuntu-22.04, gcc, g++, 3.11)	3m 23s
test-python (ubuntu-22.04, clang, clang++, 3.11)	3m 13s
test-python (macos-12, clang, clang++, 3.11)	8m 27s
cibuildwheel	17m 16s
sdist	49s
	57m 23s

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