CCACHE_DISABLE was added to bitbake.conf in oe-core dd2bab (June 2012) because
autogen-native exports HOME=/dev/null during the build, which is then used by a
host ccache to construct the path to it's cache (/dev/null/.ccache) and this
fails.
However we now always export CCACHE_DIR to solve the same problem in a more
efficient way so CCACHE_DISABLE can be deleted.
Signed-off-by: Ross Burton <ross.burton@intel.com>
