Support directories other than "web" in pub build.

sdk/lib/_internal/pub/test/build/unsupported_build_directories_test.dart

Index: sdk/lib/_internal/pub/test/build/unsupported_build_directories_test.dart
diff --git a/sdk/lib/_internal/pub/test/build/with_no_web_directory_test.dart b/sdk/lib/_internal/pub/test/build/unsupported_build_directories_test.dart
similarity index 54%
rename from sdk/lib/_internal/pub/test/build/with_no_web_directory_test.dart
rename to sdk/lib/_internal/pub/test/build/unsupported_build_directories_test.dart
index d25df7257f861a455ce60a9303937d09f4d14d02..545cc443fd4d76e3675c84b05935c5fba8af1396 100644
--- a/sdk/lib/_internal/pub/test/build/with_no_web_directory_test.dart
+++ b/sdk/lib/_internal/pub/test/build/unsupported_build_directories_test.dart
@@ -8,12 +8,13 @@ import '../test_pub.dart';
 main() {
   initConfig();
 
-  integration("with no web directory", () {
+  integration("fails if given directories are not buildable", () {
     d.appDir().create();
 
-    schedulePub(args: ["build"],
-        error: new RegExp(r'^There is no "[^"]+[/\\]web" directory.$',
-            multiLine: true),
+    schedulePub(args: ["build", "foo", "bar"],
+        error: 'Unsupported build directories "bar" and "foo".\n'
+               'The allowed directories are: "benchmark", "bin", "example", '
+                   '"test" and "web".',
         exitCode: 1);
   });
 }