-athread (pthread) / clib2

[3246251196]

athread is an option introduced during the patching.

native, pthread or single.

native uses the AmigaOS directly without any intermediate layer like clib2.

pthread uses the pthread libs. Since work is going on with clib2 (afxgroup), then should we consider some love for -athread=pthread again which would use afxgroup clib2 (at least for mcrt=clib2) ?

See also: https://github.com/sba1/adtools/issues/64.