Standardize NO_CCACHE flag and ccache definitions

[RW]

On Wed, 18 Jun 2008 22:06:21 +0300
Alex Kozlov <spam at rm-rf.kiev.ua> wrote:

> In typical case check for size and mtime is enough.

It's not really a question of good enough, if you use  the mtime of
the driver on all builds, then *every* time you rebuild the compiler,
you invaldate all the cache objects that have been built with it. That
can have a major impact on port building, and it's in things
like "portupgrade -rf gettext" where ccache is most significant. Using
the hash avoids that problem.