Make sure the CONFIGFILE variable is correct for the build when the
cache src directory is used.
Fix the build failure of kpatch-prebuilt once the actual livepatch
is added.
TestPlan:
Add the actual livepatch example patch, then build kpatch-prebuilt.
PASS: build-pkgs -c -p kpatch
PASS: build-pkgs -c -p kpatch-prebuilt -b rt,std
Story: 2009221
Task: 44580
Signed-off-by: Zhixiong Chi <zhixiong.chi@windriver.com>
Change-Id: Ia907db30a2398003c52a4f54d5f63060d7db237f
b1939418f4