tests

Disable return-type-c-linkage warning on Clang. #235

Job	Run time
tests (Mac OS 13.latest)	32s
tests (Mac OS 12.latest)	52s
tests (Centos 8, ubuntu-latest, centos8)	1m 36s
tests (Fedora 32, ubuntu-latest, fedora32)	1m 34s
tests (Fedora 33, ubuntu-latest, fedora33)	1m 41s
tests (Fedora 34, ubuntu-latest, fedora34)	1m 34s
tests (Fedora 35, ubuntu-latest, fedora35)	1m 45s
tests (Debian Testing, ubuntu-latest, debiantesting)	1m 18s
tests (Ubuntu 18.04, ubuntu-latest, ubuntu1804)	1m 13s
tests (Ubuntu 20.04, ubuntu-latest, ubuntu2004)	1m 27s
tests (Ubuntu 22.04, ubuntu-latest, ubuntu2204)	1m 12s
tests (OpenSUSE 15, ubuntu-latest, opensuse15)	1m 59s
tests (Archlinux Base (Rolling), ubuntu-latest, arch)	1m 12s
	17m 55s

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