full Android Q compat by mounting android runtime APEX

CommonInstaller

@@ -234,6 +234,9 @@ mount_partitions () {
 	SYSTEM_AS_ROOT=$(getprop ro.build.system_root_image)
 	SYSTEM_BLOCK=/dev/block/bootdevice/by-name/system
 
+	RUNTIME_APEX=""
+	APEX_LOOP=""
+
 	if [ "${SYSTEM_AS_ROOT}" == "true" ]; then
 		SLOT=$(grep_cmdline androidboot.slot_suffix)
 		if [ -n "${SLOT}" ]; then
@@ -259,6 +262,23 @@ mount_partitions () {
 
 	[ ! -f /system/build.prop ] && error "failed to mount /system (unsupported A/B device?)"
 
+	if [ -f /system/apex/com.android.runtime.apex ]; then
+		RUNTIME_APEX="/system/apex/com.android.runtime.apex"
+	elif [ -f /system/apex/com.android.runtime.release.apex ]; then
+		RUNTIME_APEX="/system/apex/com.android.runtime.release.apex"
+	fi
+
+	if [ -n "${RUNTIME_APEX}" ]; then
+		mkdir -p /dev/tmp/apex
+		unzip "${RUNTIME_APEX}" -d /dev/tmp/apex
+
+		mkdir -p /apex/com.android.runtime
+
+		mount -oloop,ro /dev/tmp/apex/apex_payload.img /apex/com.android.runtime
+
+		APEX_LOOP=$(mount | awk '/com.android.runtime/{print $1}')
+	fi
+
 	! is_mounted /vendor && mount /vendor
 
 	if [ -L /system/vendor ]; then
@@ -405,6 +425,8 @@ nanodroid_finalize () {
 	umount -l /system 2>/dev/null
 	umount -l /vendor 2>/dev/null
 	umount -l /dev/random 2>/dev/null
+	umount -l /apex/com.android.runtime 2>/dev/null
+	losetup -d ${APEX_LOOP} 2>/dev/null
 }
 
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