Allow android_aar_prebuilt info files to be ignored during update

If the update_android_aar_prebuilts gn arg is set, all info files are
updated. However, some info files could actually not be part of the repo
but instead be pulled in via cipd along with the aar itself. This cl
adds a gn template flag to disable updating info files for
android_aar_prebuilt targets that specify it.

Change-Id: I5b82b8e614ab989936834a1b270c0d97bba2da3f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2353355
Commit-Queue: Mohamed Heikal <mheikal@chromium.org>
Reviewed-by: Andrew Grieve <agrieve@chromium.org>
Cr-Commit-Position: refs/heads/master@{#797847}

build/config/android/rules.gni

@@ -4099,6 +4099,9 @@ if (enable_java_templates) {
   #   ignore_native_libraries: Whether to ignore .so files found in the .aar.
   #       See also extract_native_libraries.
   #   ignore_proguard_configs: Whether to ignore proguard configs.
+  #   ignore_info_updates: Whether to ignore the info file when
+  #       update_android_aar_prebuilts gn arg is true. However, the info file
+  #       will still be verified regardless of the value of this flag.
   #   strip_resources: Whether to ignore android resources found in the .aar.
   #   custom_package: Java package for generated R.java files.
   #   extract_assets: Whether to extract and include assets found in the .aar.
@@ -4143,9 +4146,12 @@ if (enable_java_templates) {
     _strip_resources =
         defined(invoker.strip_resources) && invoker.strip_resources
 
+    _ignore_info_updates =
+        defined(invoker.ignore_info_updates) && invoker.ignore_info_updates
+
     # Scan the AAR file and determine the resources and jar files.
     # Some libraries might not have resources; others might have two jars.
-    if (update_android_aar_prebuilts) {
+    if (!_ignore_info_updates && update_android_aar_prebuilts) {
       print("Writing " + rebase_path(_info_path, "//"))
       exec_script("//build/android/gyp/aar.py",
                   [