[Piglit] [ANNOUNCE] waffle >= 1.3 required, you may need to rerun CMake

[Chad Versace]

(If you don't use Piglit's Waffle backend, then you can safely ignore
this announcement).

(If commit dca9752 from 2014-01-10 didn't break your build, then you too
can safely this announcement).

A recent commit, dca9752, bumped Piglit's Waffle requirement from 1.2 to
1.3. This was required to add Piglit support for forward-compatible and
debug contexts.

Because CMake and pkgconfig do not get along as well as we like,
the new requirement may require your manual intervention even if
waffle >= 1.3 is installed on your system.

If commit dca9752 broke your build, *and* waffle >= 1.3 is installed
onto your system, then here are three ways to fix your problem, in order
of increasing invasiveness:

    1. Manually update the value of WAFFLE_VERSION in CMakeCache.txt to
       the version installed on your system, according to
       `pkg-config --modversion waffle-1`.

    2. Or... Remove CMakeCache.txt and rerun cmake.

    3. Or... Start with a clean slate. `rm -r` Piglit's build directory
       and rerun cmake.

Apologies for any invconveniences.

I'd like to see patches to change Piglit's CMake so that it never cached
pkg-config results, but that's quite low on my todo list right now.

-Chad