webos_oe_runmake_no_env_override.bbclass: Add another use case

Another scenario when this bbclass is needed is when a Makefile expects
to append to the CFLAGS, etc. that are passed in from the environment.

Open-webOS-DCO-1.0-Signed-off-by: Herb Kuta <herb.kuta@lge.com>
Change-Id: If70057d3f49bfa4d96f75adc87af2eea0d0bda24
Reviewed-on: https://g2g.palm.com/2132
Reviewed-by: Build Verification
Reviewed-by: Susan Montooth <susan.montooth@lge.com>
Tested-by: Susan Montooth <susan.montooth@lge.com>