- Fix build when using WITH_CCACHE_BUILD.
ccache's documentation says to set CCACHE_SLOPPINESS=time_macros and
CFLAGS+= -fpch-preprocess (it's a magic check in ccache for the string),
but doing these does not actually fix the build when files are cached.
Disabling PCH for ccache still results in an 18 second build, down from 143,
on a 12 core machine.
- While here, strip libraries with STRIP_CMD (not bumping rev as this is
not significant enough to warrant a rebuild).