Fixups for CentOS 7 which is now EOL #385

Job	Run time
pre-ci	5s
v3.0.x-gh-ubuntu20-linux-gcc-lean	2m 20s
v3.0.x-gh-ubuntu20-linux-gcc	2m 22s
v3.0.x-gh-ubuntu20-linux-gcc-reproducible	2m 26s
v3.0.x-gh-ubuntu20-linux-gcc-O2-g3	3m 14s
v3.0.x-gh-ubuntu20-linux-clang-lean	4m 44s
v3.0.x-gh-ubuntu20-linux-clang	5m 29s
v3.0.x-gh-ubuntu20-linux-clang-altlibs	11m 54s
v3.0.x-gh-ubuntu20-linux-clang-reproducible	5m 16s
v3.0.x-gh-ubuntu20-linux-clang-sanitizer	6m 40s
v3.0.x-gh-ubuntu20-linux-clang-O2-g3	6m 41s
Merge preflight	1s
Merge into upstream	0s
	51m 12s

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