Exclude DATETIME from the variables to fix errors like:
ERROR: meta-toolchain-osmo-1.0-r7 do_populate_sdk: Taskhash mismatch 0fb3116488402f87d1e4d637af229664 verses 6dda5ee949e484709fbac4a097018fc2 for meta-telephony/recipes-osmocom/meta/meta-toolchain-osmo.bb.do_populate_sdk
The notion of task- has been deprecated a long time ago. Call
it packagegroup now and for "packagegroup-osmocom" provide the
compability. This has not been compile tested.
The edison build will require a bbappend to provide packagegroup
now but I will do this once I need to build for Edison again.