clang70 not being cached by ccache in poudriere.
poudriere installed ccache dependency and symlinks were created for clang70 (I checked jail and symbolic links where created in libexec/ccache/).
firefox build log shows "/usr/local/bin/clang++70 -o ...".
It seems that ccache wrapper isn't being called to cache clang70.
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=232183 fixes ccache.