Use stable cuttlefish build if available. (#4652)

Ensures that the stable Cuttlefish build id is used if a valid build ID
(bid) is present in stable_build_info.json, else uses tip-of-tree build
id for cuttlefish devices.

Author: aditya-wazir

src/clusterfuzz/_internal/platforms/android/fetch_artifact.py

@@ -210,7 +210,13 @@ def get_latest_artifact_info(branch, target, signed=False):
   # TODO(https://github.com/google/clusterfuzz/issues/3950)
   # After stabilizing the Cuttlefish image, revert this
   if environment.is_android_cuttlefish():
-    return get_stable_build_info()
+    build_info = get_stable_build_info()
+    # Use tip-of-tree build if 'bid' is missing or 0.
+    # Setting 'bid' to 0 in stable_build_info.json
+    # allows for easy switching between stable build
+    # and tip-of-tree builds.
+    if 'bid' in build_info and build_info['bid'] != '0':
+      return build_info
 
   request = client.build().list(  # pylint: disable=no-member
       buildType='submitted',