Support cached images for cloud runner. (#690)

Also fix the Docker image existence check to properly check remote
registries.

experiment/builder_runner.py

@@ -905,12 +905,22 @@ def build_and_run_cloud(
         f'--upload_coverage={coverage_path}',
         f'--upload_reproducer={reproducer_path}',
         f'--upload_corpus={corpus_path}',
-        f'--experiment_name={self.experiment_name}'
+        f'--experiment_name={self.experiment_name}',
+        f'--real_project={project_name}',
     ]
+
+    if oss_fuzz_checkout.ENABLE_CACHING and (
+        oss_fuzz_checkout.is_image_cached(project_name, 'address') and
+        oss_fuzz_checkout.is_image_cached(project_name, 'coverage')):
+      logger.info(f'Using cached image for {project_name}.')
+      command.append('--use_cached_image')
+
     if cloud_build_tags:
       command += ['--tags'] + cloud_build_tags
     command += ['--'] + self._libfuzzer_args()
 
+    logger.info(f'Command: {command}')
+
     if not self._run_with_retry_control(os.path.realpath(target_path),
                                         command,
                                         cwd=oss_fuzz_checkout.OSS_FUZZ_DIR):

experiment/oss_fuzz_checkout.py

@@ -30,7 +30,7 @@
 
 BUILD_DIR: str = 'build'
 GLOBAL_TEMP_DIR: str = ''
-ENABLE_CACHING = bool(int(os.getenv('OFG_USE_CACHING', '0')))
+ENABLE_CACHING = bool(int(os.getenv('OFG_USE_CACHING', '1')))
 # Assume OSS-Fuzz is at repo root dir by default.
 # This will change if temp_dir is used.
 OSS_FUZZ_DIR: str = os.path.join(
@@ -285,7 +285,7 @@ def is_image_cached(project_name: str, sanitizer: str) -> bool:
   cached_image_name = _get_project_cache_image_name(project_name, sanitizer)
   try:
     sp.run(
-        ['docker', 'inspect', '--type=image', cached_image_name],
+        ['docker', 'manifest', 'inspect', cached_image_name],
         check=True,
         stdin=sp.DEVNULL,
         stdout=sp.DEVNULL,