libsepol/src/Makefile: fix reallocarray detection #537

Job	Run time
build (gcc, 3.11, 3.1)	1m 27s
build (gcc, 3.11, 3.1, test-flags-override)	2m 8s
build (gcc, 3.11, 3.1, test-debug)	2m 14s
build (gcc, 3.11, 3.1, linker-bfd)	1m 51s
build (gcc, 3.11, 3.1, linker-gold)	1m 45s
build (gcc, 3.10, 3.1)	1m 30s
build (gcc, 3.9, 3.1)	1m 30s
build (gcc, 3.8, 3.1)	1m 36s
build (gcc, 3.7, 3.1)	1m 50s
build (gcc, pypy3.7, 3.1)	2m 13s
build (gcc, 3.11, 3.0)	1m 35s
build (gcc, 3.11, 2.7)	2m 3s
build (gcc, 3.11, 2.6)	1m 39s
build (gcc, 3.11, 2.5)	2m 16s
build (clang, 3.11, 3.1)	1m 31s
build (clang, 3.11, 3.1, test-flags-override)	1m 27s
build (clang, 3.11, 3.1, test-debug)	1m 25s
build (clang, 3.10, 3.1)	1m 39s
build (clang, 3.9, 3.1)	2m 14s
build (clang, 3.8, 3.1)	2m 8s
build (clang, 3.7, 3.1)	2m 42s
build (clang, pypy3.7, 3.1)	2m 34s
build (clang, 3.11, 3.0)	1m 28s
build (clang, 3.11, 2.7)	1m 47s
build (clang, 3.11, 2.6)	2m 41s
build (clang, 3.11, 2.5)	1m 53s
build (gcc, 3.11, 3.1, sanitizers)	1m 53s
	50m 59s

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