ci: update lint workflow, fix caching #65

Job	Run time
setup	24s
simple-build	8s
simple-build (-skip-unused)	6s
lint / fmt	9s
test	9s
setup-clang	2m 23s
different-compilers (gcc)	30s
different-compilers (gcc, -prod)	42s
different-compilers (gcc, -skip-unused)	26s
different-compilers (gcc, -skip-unused, -prod)	37s
different-compilers (clang)	49s
different-compilers (clang, -prod)	46s
different-compilers (clang, -skip-unused)	49s
different-compilers (clang, -skip-unused, -prod)	54s
clang-sanitizers (address)	1m 1s
clang-sanitizers (memory)	1m 25s
clang-sanitizers (undefined)	1m 12s
clang-sanitizers (leak)	1m 10s
gcc-undefined-sanitizers	39s
gcc-address-sanitizers	43s
gcc-sanitizers (leak)	24s
	15m 26s

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