Add ppc64le to CI and fix node20 breakage #98

Job	Run time
posix (Collect coverage 1, yes, gcc-12, 20, ubuntu-22.04, g++-12-multilib, 64, arithmetic_tests)	54m 15s
posix (Collect coverage 2, yes, gcc-12, 20, ubuntu-22.04, g++-12-multilib, 64, cpp_int_tests)	21m 13s
posix (Collect coverage 3, yes, gcc-12, 20, ubuntu-22.04, g++-12-multilib, 64, functions_and_limits)	20m 13s
posix (Collect coverage 4, yes, gcc-12, 20, ubuntu-22.04, g++-12-multilib, 64, conversions)	12m 27s
posix (Collect coverage 5, yes, gcc-12, 20, ubuntu-22.04, g++-12-multilib, 64, performance)	16m 22s
posix (Collect coverage 6, yes, gcc-12, 20, ubuntu-22.04, g++-12-multilib, 64, misc)	24m 18s
posix (Collect coverage 7, yes, gcc-12, 20, ubuntu-22.04, g++-12-multilib, 64, compile_fail)	4m 37s
posix (Collect coverage 8, yes, gcc-12, 20, ubuntu-22.04, g++-12-multilib, 64, examples)	24m 54s
posix (Collect coverage 9, yes, gcc-12, 20, ubuntu-22.04, g++-12-multilib, 64, concepts)	2m 11s
	3h 0m 30s

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