Fix some web tool pub issues (#1291)

.github/workflows/gh-pages.yml

@@ -6,7 +6,7 @@ permissions: read-all
 on:
   push:
     branches:
-      - master
+      - main
 jobs:
   build-and-deploy:
     permissions:

web/_tool/build_ci.dart

@@ -17,8 +17,8 @@ main() async {
   ];
 
   print('Building the sample index...');
-  await _run('samples_index', 'pub', ['get']);
+  await _run('samples_index', 'flutter', ['pub', 'get']);
-  await _run('samples_index', 'pub', ['run', 'grinder', 'deploy']);
+  await _run('samples_index', 'flutter', ['pub', 'run', 'grinder', 'deploy']);
 
   // Create the directory each Flutter Web sample lives in
   Directory(p.join(Directory.current.path, 'samples_index', 'public', 'web'))

web/_tool/peanut_post_build.dart

@@ -42,8 +42,8 @@ main(List<String> args) async {
 
   // Build the sample index and copy the files into this directory
   print('building the sample index...');
-  await run('samples_index', 'pub', ['get']);
+  await run('samples_index', 'flutter', ['pub', 'get']);
-  await run('samples_index', 'pub', ['run', 'grinder', 'deploy']);
+  await run('samples_index', 'flutter', ['pub', 'run', 'grinder', 'deploy']);
 
   // Copy the contents of the samples_index/public directory to the build
   // directory