There are GKI arm64 and x86_64 now. The patch restructures the
GKI common settings to a new common BoardConfig file
"BoardConfigGkiCommon.mk".
It includes the ramdisk and boot image settings for GKI.
The patch also removes obsolete TARGET_PRELINK_MODULE.
Bug: 177859525
Bug: 181277965
Test: lunch gsi_arm64-userdebug ; make dist
Test: lunch gsi_x86_64-userdebug ; make dist
Change-Id: I204c8937d97140cc3c6ed3473d494f03f534ed75
