[OE-core] [PATCH 0/2] bitbake.conf: gracefully work with ccache environment variables

[Jason Wessel]

The end user of oe-core should be free to turn off ccache, or use an
external ccache without impacting the sstate sums.

Example of using a different ccache directory via local.conf

CCACHE_DIR = "/tmp/ccache"

Example of turning off ccache:

export CCACHE_DISABLE = "1"
BB_HASHBASE_WHITELIST += "CCACHE_DISABLE"

Jason.