Android: Fix list_java_targets.py if run after "gn clean"

Bug: 385968364
Change-Id: Icfdc6b2a77af0accd6ef3d3a8c82be217324ef6c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6164812
Auto-Submit: Andrew Grieve <[email protected]>
Reviewed-by: Shuhei Takahashi <[email protected]>
Commit-Queue: Andrew Grieve <[email protected]>
Cr-Commit-Position: refs/heads/main@{#1405862}
diff --git a/build/android/list_java_targets.py b/build/android/list_java_targets.py
index 309b33a..aeca42ef 100755
--- a/build/android/list_java_targets.py
+++ b/build/android/list_java_targets.py
@@ -234,10 +234,17 @@
   constants.CheckOutputDirectory()
   output_dir = constants.GetOutDirectory()
 
+  if args.build:
+    _compile(output_dir, ['build.ninja'])
+
   # Query ninja for all __build_config_crbug_908819 targets.
   targets = _query_for_build_config_targets(output_dir)
   entries = [_TargetEntry(t) for t in targets]
 
+  if not entries:
+    logging.warning('No targets found. Run with --build')
+    sys.exit(1)
+
   if args.build:
     logging.warning('Building %d .build_config.json files...', len(entries))
     _compile(output_dir, [e.ninja_build_config_target for e in entries],