[ci] Split android-platform_tests in 2 shards (#2577)

.cirrus.yml

@@ -182,6 +182,9 @@ task:
     ### Android tasks ###
     - name: android-platform_tests
       env:
+        matrix:
+          PACKAGE_SHARDING: "--shardIndex 0 --shardCount 2"
+          PACKAGE_SHARDING: "--shardIndex 1 --shardCount 2"
         matrix:
           CHANNEL: "master"
           CHANNEL: "stable"

script/tool_runner.sh

@@ -8,6 +8,9 @@ SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" >/dev/null && pwd)"
 REPO_DIR="$(dirname "$SCRIPT_DIR")"
 
 # The tool expects to be run from the repo root.
+# PACKAGE_SHARDING is (optionally) set from Cirrus. See .cirrus.yml
 cd "$REPO_DIR"
-dart pub global run flutter_plugin_tools "$@" --packages-for-branch \
-  --log-timing $BUILD_SHARDING
+dart pub global run flutter_plugin_tools "$@" \
+  --packages-for-branch \
+  --log-timing \
+  $PACKAGE_SHARDING