libselinux: constify avc_open(3) parameter #574

Job	Run time
build (gcc, 3.12, 3.3)	1m 45s
build (gcc, 3.12, 3.3, test-flags-override)	1m 33s
build (gcc, 3.12, 3.3, test-debug)	1m 25s
build (gcc, 3.12, 3.3, linker-bfd)	1m 33s
build (gcc, 3.12, 3.3, linker-gold)	1m 32s
build (gcc, 3.11, 3.3)	1m 34s
build (gcc, 3.10, 3.3)	2m 0s
build (gcc, 3.9, 3.3)	1m 36s
build (gcc, 3.8, 3.3)	1m 42s
build (gcc, 3.7, 3.3)	1m 43s
build (gcc, pypy3.7, 3.3)	2m 38s
build (gcc, 3.12, 3.2)	1m 33s
build (gcc, 3.12, 3.1)	1m 33s
build (gcc, 3.12, 3.0)	1m 36s
build (gcc, 3.12, 2.7)	2m 8s
build (gcc, 3.12, 2.6)	1m 48s
build (gcc, 3.12, 2.5)	1m 59s
build (clang, 3.12, 3.3)	1m 44s
build (clang, 3.12, 3.3, test-flags-override)	1m 30s
build (clang, 3.12, 3.3, test-debug)	1m 28s
build (clang, 3.11, 3.3)	1m 43s
build (clang, 3.10, 3.3)	1m 36s
build (clang, 3.9, 3.3)	1m 43s
build (clang, 3.8, 3.3)	1m 41s
build (clang, 3.7, 3.3)	1m 59s
build (clang, pypy3.7, 3.3)	2m 13s
build (clang, 3.12, 3.2)	1m 47s
build (clang, 3.12, 3.1)	1m 45s
build (clang, 3.12, 3.0)	1m 35s
build (clang, 3.12, 2.7)	1m 55s
build (clang, 3.12, 2.6)	1m 52s
build (clang, 3.12, 2.5)	2m 32s
build (gcc, 3.12, 3.3, sanitizers)	2m 0s
	58m 41s

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