pmbootstrap: enable ccache when using distcc to cross compile
Created by: zhuowei
Based on https://wiki.gentoo.org/wiki/Distcc#With_automake.
Compile time of weston is shortened from 11 minutes on first compile to 10 minutes on second.
This doesn't work for kwin, though - using this configuration cmake only builds with ccache and not distcc. Sigh. I don't known enough about cmake, distcc, and ccache: how would I start fixing this?
Note that I haven't checked if this actually speeds things up relative to the original code, and I'll rather not spend another 30 minutes building Weston, so I would really appreciate if someone can see if this actually has an effect.
This fixes issue #716 (closed).