sepolgen-ifgen: allow M4 escaped filenames #149

Job	Run time
build (gcc, 3.12, 3.3)	1s
build (gcc, 3.12, 3.3, test-flags-override)	1s
build (gcc, 3.12, 3.3, test-debug)	1s
build (gcc, 3.12, 3.3, linker-bfd)	1s
build (gcc, 3.12, 3.3, linker-gold)	1s
build (gcc, 3.11, 3.3)	23s
build (gcc, 3.10, 3.3)	24s
build (gcc, 3.9, 3.3)	1s
build (gcc, 3.8, 3.3)	1s
build (gcc, 3.7, 3.3)	1s
build (gcc, pypy3.7, 3.3)	1s
build (gcc, 3.12, 3.2)	1s
build (gcc, 3.12, 3.1)	1s
build (gcc, 3.12, 3.0)	1s
build (gcc, 3.12, 2.7)	12s
build (gcc, 3.12, 2.6)	10s
build (gcc, 3.12, 2.5)	13s
build (clang, 3.12, 3.3)	26s
build (clang, 3.12, 3.3, test-flags-override)	25s
build (clang, 3.12, 3.3, test-debug)	23s
build (clang, 3.11, 3.3)	27s
build (clang, 3.10, 3.3)	26s
build (clang, 3.9, 3.3)	25s
build (clang, 3.8, 3.3)	20s
build (clang, 3.7, 3.3)	6s
build (clang, pypy3.7, 3.3)	13s
build (clang, 3.12, 3.2)	27s
build (clang, 3.12, 3.1)	25s
build (clang, 3.12, 3.0)	26s
build (clang, 3.12, 2.7)	13s
build (clang, 3.12, 2.6)	14s
build (clang, 3.12, 2.5)	15s
build (gcc, 3.12, 3.3, sanitizers)	1s
	6m 46s

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