libselinux: constify avc_open(3) parameter #185

Job	Run time
build (gcc, 3.12, 3.3)	1m 43s
build (gcc, 3.12, 3.3, test-flags-override)	1m 21s
build (gcc, 3.12, 3.3, test-debug)	1m 22s
build (gcc, 3.12, 3.3, linker-bfd)	1m 32s
build (gcc, 3.12, 3.3, linker-gold)	1m 37s
build (gcc, 3.11, 3.3)	1m 32s
build (gcc, 3.10, 3.3)	1m 37s
build (gcc, 3.9, 3.3)	1m 33s
build (gcc, 3.8, 3.3)	1m 34s
build (gcc, 3.7, 3.3)	1m 40s
build (gcc, pypy3.7, 3.3)	2m 7s
build (gcc, 3.12, 3.2)	1m 33s
build (gcc, 3.12, 3.1)	1m 28s
build (gcc, 3.12, 3.0)	1m 35s
build (gcc, 3.12, 2.7)	1m 44s
build (gcc, 3.12, 2.6)	1m 53s
build (gcc, 3.12, 2.5)	1m 50s
build (clang, 3.12, 3.3)	1m 41s
build (clang, 3.12, 3.3, test-flags-override)	1m 45s
build (clang, 3.12, 3.3, test-debug)	1m 29s
build (clang, 3.11, 3.3)	1m 44s
build (clang, 3.10, 3.3)	1m 41s
build (clang, 3.9, 3.3)	1m 45s
build (clang, 3.8, 3.3)	1m 47s
build (clang, 3.7, 3.3)	1m 53s
build (clang, pypy3.7, 3.3)	2m 3s
build (clang, 3.12, 3.2)	1m 49s
build (clang, 3.12, 3.1)	1m 41s
build (clang, 3.12, 3.0)	1m 42s
build (clang, 3.12, 2.7)	1m 59s
build (clang, 3.12, 2.6)	1m 48s
build (clang, 3.12, 2.5)	1m 47s
build (gcc, 3.12, 3.3, sanitizers)	2m 32s
	56m 47s

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