Bump build_runner to 2.5.x for faster builds (#9268)

Author: srawlins

packages/devtools_app/pubspec.yaml

@@ -61,7 +61,7 @@ dependencies:
 
 dev_dependencies:
   args: ^2.4.2
-  build_runner: ^2.3.3
+  build_runner: ^2.5.4
   devtools_test:
     path: ../devtools_test
   fake_async: ^1.3.1
@@ -78,6 +78,11 @@ dev_dependencies:
   web_benchmarks: ^4.0.0
   webkit_inspection_protocol: ">=0.5.0 <2.0.0"
 
+dependency_overrides:
+  # Necessary while `stager` dep disallows `source_gen` 2.0.0. Remove when
+  # `stager` allows `source_gen` 2.0.0.
+  source_gen: ^2.0.0
+
 flutter:
   uses-material-design: true
   assets:

pubspec.yaml

@@ -13,5 +13,5 @@ workspace:
   - tool
 
 dev_dependencies:
-  build_runner: ^2.3.3
+  build_runner: ^2.5.4
   flutter_lints: ^5.0.0