C CI

.github/workflows/c.yml: first go at controlling parallel builds #75

Job	Run time
ubuntu-latest bmake CC=gcc NO_SANI=yes MKDOC=yes	14s
ubuntu-latest bmake CC=gcc USE_ASAN=yes MKDOC=yes	12s
ubuntu-latest bmake CC=gcc USE_UBSAN=yes MKDOC=yes	13s
ubuntu-latest bmake CC=gcc USE_LEAKSAN=yes MKDOC=yes	11s
ubuntu-latest bmake CC=clang NO_SANI=yes MKDOC=yes	14s
ubuntu-latest bmake CC=clang USE_ASAN=yes MKDOC=yes	12s
ubuntu-latest bmake CC=clang USE_UBSAN=yes MKDOC=yes	12s
ubuntu-latest bmake CC=clang USE_LEAKSAN=yes MKDOC=yes	13s
ubuntu-20.04 bmake CC=gcc NO_SANI=yes MKDOC=no	17s
ubuntu-20.04 bmake CC=gcc USE_ASAN=yes MKDOC=no	19s
ubuntu-20.04 bmake CC=gcc USE_UBSAN=yes MKDOC=no	23s
ubuntu-20.04 bmake CC=gcc USE_LEAKSAN=yes MKDOC=no	16s
ubuntu-20.04 bmake CC=clang NO_SANI=yes MKDOC=no	23s
ubuntu-20.04 bmake CC=clang USE_ASAN=yes MKDOC=no	24s
ubuntu-20.04 bmake CC=clang USE_UBSAN=yes MKDOC=no	29s
ubuntu-20.04 bmake CC=clang USE_LEAKSAN=yes MKDOC=no	21s
macos-latest bmake CC=clang NO_SANI=yes MKDOC=no	49s
macos-latest bmake CC=clang USE_ASAN=yes MKDOC=no	1m 5s
macos-latest bmake CC=clang USE_UBSAN=yes MKDOC=no	1m 38s
macos-latest bmake CC=clang USE_LEAKSAN=yes MKDOC=no	1m 1s
macos-11 bmake CC=clang NO_SANI=yes MKDOC=no	2m 52s
macos-11 bmake CC=clang USE_ASAN=yes MKDOC=no	2m 37s
macos-11 bmake CC=clang USE_UBSAN=yes MKDOC=no	2m 49s
macos-11 bmake CC=clang USE_LEAKSAN=yes MKDOC=no	2m 36s
	20m 0s

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