Add support for RHEL 8 #21

Job	Run time
cleanup (debian-bookworm)	26s
cleanup (debian-bullseye)	10s
cleanup (rhel-10)	5s
cleanup (gcc)	9s
cleanup (tools-rippled-documentation)	6s
cleanup (tools-rippled-prettier)	5s
cleanup (ubuntu-jammy)	7s
cleanup (rhel-8)	6s
cleanup (tools-rippled-pre-commit)	4s
cleanup (tools-rippled-clang-format)	6s
cleanup (ubuntu-noble)	32s
cleanup (rhel-9)	17s
	2m 13s

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