validate_target_files: support gki_arm64

gki_arm64 is a special target to build multiple GKI boot-*.img
files. It has neither system.img nor vbmeta.img. Skips checking
system.img and vbmeta.img in this case.

Bug: 223078405
Test: validate_target_files signed-gki_arm64-target_files-8277156.zip
Change-Id: I9d3c102c11787cf70c1e1fc8e6a552f8fd19ff72
diff --git a/tools/releasetools/validate_target_files.py b/tools/releasetools/validate_target_files.py
index 282dc99..beb9e75 100755
--- a/tools/releasetools/validate_target_files.py
+++ b/tools/releasetools/validate_target_files.py
@@ -131,8 +131,10 @@
     logging.warning('Skipped due to target using non-sparse images')
     return
 
-  # Verify IMAGES/system.img.
-  CheckAllFiles('system')
+  # Verify IMAGES/system.img if applicable.
+  # Some targets, e.g., gki_arm64, gki_x86_64, etc., are system.img-less.
+  if 'IMAGES/system.img' in input_zip.namelist():
+    CheckAllFiles('system')
 
   # Verify IMAGES/vendor.img if applicable.
   if 'VENDOR/' in input_zip.namelist():
@@ -259,9 +261,6 @@
 
 def ValidatePartitionFingerprints(input_tmp, info_dict):
   build_info = common.BuildInfo(info_dict)
-  if not build_info.avb_enabled:
-    logging.info("AVB not enabled, skipping partition fingerprint checks")
-    return
   # Expected format:
   #  Prop: com.android.build.vendor.fingerprint -> 'generic/aosp_cf_x86_64_phone/vsoc_x86_64:S/AOSP.MASTER/7335886:userdebug/test-keys'
   #  Prop: com.android.build.vendor_boot.fingerprint -> 'generic/aosp_cf_x86_64_phone/vsoc_x86_64:S/AOSP.MASTER/7335886:userdebug/test-keys'
@@ -398,7 +397,7 @@
           verity_key_mincrypt, stdoutdata.rstrip())
 
   # Handle the case of Verified Boot 2.0 (AVB).
-  if info_dict.get("avb_enable") == "true":
+  if info_dict.get("avb_building_vbmeta_image") == "true":
     logging.info('Verifying Verified Boot 2.0 (AVB) images...')
 
     key = options['verity_key']