checkpolicy/oss-fuzz: add libfuzz based fuzzer #538

Job	Run time
build (gcc, 3.11, 3.1)	1m 34s
build (gcc, 3.11, 3.1, test-flags-override)	1m 20s
build (gcc, 3.11, 3.1, test-debug)	1m 17s
build (gcc, 3.11, 3.1, linker-bfd)	1m 28s
build (gcc, 3.11, 3.1, linker-gold)	1m 49s
build (gcc, 3.10, 3.1)	1m 29s
build (gcc, 3.9, 3.1)	1m 37s
build (gcc, 3.8, 3.1)	1m 28s
build (gcc, 3.7, 3.1)	1m 38s
build (gcc, pypy3.7, 3.1)	1m 47s
build (gcc, 3.11, 3.0)	1m 34s
build (gcc, 3.11, 2.7)	2m 17s
build (gcc, 3.11, 2.6)	1m 34s
build (gcc, 3.11, 2.5)	1m 36s
build (clang, 3.11, 3.1)	1m 34s
build (clang, 3.11, 3.1, test-flags-override)	1m 18s
build (clang, 3.11, 3.1, test-debug)	1m 17s
build (clang, 3.10, 3.1)	2m 7s
build (clang, 3.9, 3.1)	1m 38s
build (clang, 3.8, 3.1)	1m 32s
build (clang, 3.7, 3.1)	1m 45s
build (clang, pypy3.7, 3.1)	2m 2s
build (clang, 3.11, 3.0)	1m 29s
build (clang, 3.11, 2.7)	2m 9s
build (clang, 3.11, 2.6)	2m 5s
build (clang, 3.11, 2.5)	1m 56s
build (gcc, 3.11, 3.1, sanitizers)	1m 56s
	45m 16s

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