Cache the compiler output of rust code with sccache, like we use ccache
for c code.
I've considered using sccache to completely replace ccache since it can
cache output of C/C++ code too. But let's not do it for now since ccache
doesn't need to run a daemon in the background that needs to be stopped
when shutting down / zapping. Also it would need more refactoring.
Reviewed-by: Luca Weiss <luca@z3ntu.xyz>
Link: https://lists.sr.ht/~postmarketos/pmbootstrap-devel/%3C20230806184729.4891-5-ollieparanoid@postmarketos.org%3E
147a0f5c4d