C CI

Makefile: try avoiding parallel builds for older sjg Mk-files #74

Job	Run time
ubuntu-latest bmake CC=gcc NO_SANI=yes MKDOC=yes	15s
ubuntu-latest bmake CC=gcc USE_ASAN=yes MKDOC=yes	15s
ubuntu-latest bmake CC=gcc USE_UBSAN=yes MKDOC=yes	16s
ubuntu-latest bmake CC=gcc USE_LEAKSAN=yes MKDOC=yes	14s
ubuntu-latest bmake CC=clang NO_SANI=yes MKDOC=yes	26s
ubuntu-latest bmake CC=clang USE_ASAN=yes MKDOC=yes	14s
ubuntu-latest bmake CC=clang USE_UBSAN=yes MKDOC=yes	11s
ubuntu-latest bmake CC=clang USE_LEAKSAN=yes MKDOC=yes	12s
ubuntu-20.04 bmake CC=gcc NO_SANI=yes MKDOC=no	13s
ubuntu-20.04 bmake CC=gcc USE_ASAN=yes MKDOC=no	25s
ubuntu-20.04 bmake CC=gcc USE_UBSAN=yes MKDOC=no	13s
ubuntu-20.04 bmake CC=gcc USE_LEAKSAN=yes MKDOC=no	17s
ubuntu-20.04 bmake CC=clang NO_SANI=yes MKDOC=no	14s
ubuntu-20.04 bmake CC=clang USE_ASAN=yes MKDOC=no	17s
ubuntu-20.04 bmake CC=clang USE_UBSAN=yes MKDOC=no	26s
ubuntu-20.04 bmake CC=clang USE_LEAKSAN=yes MKDOC=no	13s
macos-latest bmake CC=clang NO_SANI=yes MKDOC=no	1m 11s
macos-latest bmake CC=clang USE_ASAN=yes MKDOC=no	47s
macos-latest bmake CC=clang USE_UBSAN=yes MKDOC=no	1m 18s
macos-latest bmake CC=clang USE_LEAKSAN=yes MKDOC=no	48s
macos-11 bmake CC=clang NO_SANI=yes MKDOC=no	2m 42s
macos-11 bmake CC=clang USE_ASAN=yes MKDOC=no	2m 51s
macos-11 bmake CC=clang USE_UBSAN=yes MKDOC=no	2m 43s
macos-11 bmake CC=clang USE_LEAKSAN=yes MKDOC=no	2m 45s
	19m 26s

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