Add `sme`/`sme2` detection to `mach/init.c` #395

Job	Run time
cmake-linux-riscv64	7s
cmake-darwin	27s
cmake-android (android-arm64-build.sh)	1m 47s
cmake-linux-local	45s
cmake-android (android-armv7-build.sh)	2m 26s
cmake-uwp	1m 49s
cmake-android (android-riscv64-build.sh)	55s
cmake-windows	1m 59s
cmake-android (android-x86-build.sh)	1m 6s
	11m 21s

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