Add build_gki_apex_manifest.

This is a helper host binary to build APEX manifest for
GKI APEXes as well as checking the boot image against the
declared KMI version.

Test: build GKI APEX
Bug: 168255100
Bug: 161563386
Change-Id: I6559b3125345cc05783076daec472c95834997e1
4 files changed