Fix the build for M1 MacBooks

[jwatte]

It turns out, MACOS is a perfectly fine OS to support aarch64 (through its name arm64.)

The only thing missing was the appropriate check in impl_aarch64, plus renaming the file to match that it's really for any OS that has the CPU.

jwatte@Jons-MBP build % make test Running tests... Test project /Users/jwatte/cpu_features/build Start 1: bit_utils_test 1/4 Test #1: bit_utils_test ................... Passed 0.06 sec Start 2: string_view_test 2/4 Test #2: string_view_test ................. Passed 0.04 sec Start 3: stack_line_reader_test 3/4 Test #3: stack_line_reader_test ........... Passed 0.04 sec Start 4: cpuinfo_aarch64_test 4/4 Test #4: cpuinfo_aarch64_test ............. Passed 0.12 sec

[jwatte]

Also, I have signed the CLA, and trying to re-sign it gives me an error saying it's already signed.

[toor1245]

@gchatelet, can we close this PR, since we will be adding changes to fix the build for M1 in the future?

[testn]

Can we get this fixed, please? It has been broken for a long time.

[technicalpickles]

I think this can be closed now that https://github.com/google/cpu_features/pull/209 merged which makes a similar fix

[Mizux]

closing it as duplicate of the on going PR:

• #204