checkpolicy/oss-fuzz: add libfuzz based fuzzer #539

Job	Run time
build (gcc, 3.11, 3.1)	1m 29s
build (gcc, 3.11, 3.1, test-flags-override)	1m 49s
build (gcc, 3.11, 3.1, test-debug)	1m 32s
build (gcc, 3.11, 3.1, linker-bfd)	1m 42s
build (gcc, 3.11, 3.1, linker-gold)	1m 24s
build (gcc, 3.10, 3.1)	1m 26s
build (gcc, 3.9, 3.1)	1m 55s
build (gcc, 3.8, 3.1)	1m 31s
build (gcc, 3.7, 3.1)	1m 36s
build (gcc, pypy3.7, 3.1)	1m 53s
build (gcc, 3.11, 3.0)	1m 32s
build (gcc, 3.11, 2.7)	1m 47s
build (gcc, 3.11, 2.6)	2m 6s
build (gcc, 3.11, 2.5)	1m 43s
build (clang, 3.11, 3.1)	1m 38s
build (clang, 3.11, 3.1, test-flags-override)	1m 46s
build (clang, 3.11, 3.1, test-debug)	1m 26s
build (clang, 3.10, 3.1)	1m 33s
build (clang, 3.9, 3.1)	1m 31s
build (clang, 3.8, 3.1)	2m 3s
build (clang, 3.7, 3.1)	1m 45s
build (clang, pypy3.7, 3.1)	1m 57s
build (clang, 3.11, 3.0)	1m 33s
build (clang, 3.11, 2.7)	2m 9s
build (clang, 3.11, 2.6)	1m 56s
build (clang, 3.11, 2.5)	1m 40s
build (gcc, 3.11, 3.1, sanitizers)	1m 58s
	46m 20s

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