Support directories other than "web" in pub build.

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

Index: sdk/lib/_internal/pub/test/build/handles_long_paths_test.dart
diff --git a/sdk/lib/_internal/pub/test/build/handles_long_paths_test.dart b/sdk/lib/_internal/pub/test/build/handles_long_paths_test.dart
index ab99924f91262a2498593b55985a17f70eaf5d61..bac6d725f402c0e9305dceac23fb4bc3edac54e6 100644
--- a/sdk/lib/_internal/pub/test/build/handles_long_paths_test.dart
+++ b/sdk/lib/_internal/pub/test/build/handles_long_paths_test.dart
@@ -60,10 +60,12 @@ main() {
 
     d.dir(appPath, [
       d.dir('build', [
-        d.file("index.html", "html"),
-        d.dir('assets', [
-          d.dir('foo', [
-            d.file('foo.txt', 'foo')
+        d.dir('web', [
+          d.file("index.html", "html"),
+          d.dir('assets', [
+            d.dir('foo', [
+              d.file('foo.txt', 'foo')
+            ])
           ])
         ])
       ])