Fix-ups for macOS

[barracuda156]

1. Precompiled headers target is wrong in CMake and breaks the build with GCC:
   https://gitlab.kitware.com/cmake/cmake/-/issues/25656
   https://gitlab.kitware.com/cmake/cmake/-/issues/25514

2. <unistd.h> is missing.

3. AudioComponent* stuff is in AudioUnit framework, at least on some systems:
   https://github.com/phracker/MacOSX-SDKs/blob/master/MacOSX10.8.sdk/System/Library/Frameworks/AudioUnit.framework/Versions/A/Headers/AudioComponent.h

[barracuda156]

And just in case, while linking to AudioUnit may not be required on the latest macOS versions, it works fine:

[100%] Linking CXX executable abaddon
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/opt/local/lib/libsodium.dylib
ld: warning: reexported library with install name '/opt/local/lib/libunwind.1.dylib' found at '/opt/local/lib/libunwind.1.dylib' couldn't be matched with any parent library and will be linked directly
make[2]: Leaving directory `/opt/local/var/macports/build/_opt_svacchanda_SonomaPorts_net_abaddon/abaddon/work/build'
[100%] Built target abaddon

This is on Sonoma / aarch64

[barracuda156]

@ouwou Thank you for merging!