Introduced build mtime cache structure. Reset it before the build
to prevent bitbake from crashing when build/tmp/stamps hierarchy
is removed.
[YOCTO: #7562]
(Bitbake rev: f8590547a198a78334debdf14bf40acb50c22ecc)
Signed-off-by: Ed Bartosh <ed.bartosh@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>