sstatesig: Improve the support for locked down sstate cache usage
Add code in the sstate hash validation code to ensure it really did
install these from sstate since if it didn't should to warn/abort
the build. The judgment condition is:
1) If a build is replaced by locked sstate-cache, it will triger a
warn/error;
2) If objects are not used from the locked cache, it will triger a
warn/error;
3) Use SIGGEN_LOCKEDSIGS_CHECK_LEVEL variable controls whether this
is just a warning or a fatal error or nothing to report.
[YOCTO #6639]
(From OE-Core rev:
305912dce61c4fed0cbf631aa98a9e6f29db88e4)
Signed-off-by: Hongxu Jia <hongxu.jia@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
