fix(build): make perf tests work again

scripts/ci/env_dart.sh

@@ -70,6 +70,7 @@ if [[ -z $ENV_SET ]]; then
   export DARTSDK
   export DART
   export PUB=${PUB:-"$DART_SDK/bin/pub"}
+  export PUB_CACHE=$DART_SDK/pub-cache
   export DARTANALYZER=${DARTANALYZER:-"$DART_SDK/bin/dartanalyzer"}
   export DARTDOC=${DARTDOC:-"$DART_SDK/bin/dartdoc"}
   export DART_DOCGEN=${DART_DOCGEN:-"$DART_SDK/bin/docgen"}