Fix building for ARM-based macOS

[NeRdTheNed]

• Fixed a typo in the arch flags
• Changed the signature of the zlib ARM crc32 implementation to match the exported zlib signature

[fhanau]

Implemented the fix. Note that changing the function signature of the ARM crc32 in this case actually causes the checksum to be corrupted, perhaps because it changes the return value from 32 to 64 bits. Of course having mismatching function signatures should be avoided, but for now removing the header containing the function prototype for ARM fixes the compilation and does not result in invalid signatures.
I will develop a proper patch later on.