[ccache] New GCC option which decreases ccache lookup times

[Ollie Wild]

This is just a heads up to the ccache community about a new option
I've added to GCC which reduces the time to perform ccache lookups.
Starting with GCC 4.3, executing

        ccache <compiler> -fdirectives-only [OPTIONS]

will cause ccache to use a partially preprocessed source file in its
lookup.  It is about 30% faster to generate the partially preprocessed
source than it is to perform full preprocessing.  However, it comes at
a slight cost: the time taken to perform the initial compilation via
ccache is increased.

A more detailed description can be found at
http://gcc.gnu.org/ml/gcc-patches/2007-02/msg01098.html.

Feel free to try out the latest GCC trunk and send me any feedback you
may have.  I am not on the ccache mailing list, so please cc me on any
replies.

Ollie