fix(@angular-devkit/build-angular): avoid undefined module path for Sass imports in esbuild

When using Sass with the experimental esbuild-based browser application builder, bare imports
without a path segment that were available via included paths but also happen to be a node module
could cause an exception. An example of such an import would be `@import "globals";`. The deep
import node module logic would previously attempt to join an undefined path segment to the resolved
path for the `globals` package which would raise a argument type exception. This case has now been
fixed by only joining if there is actually a path segment present such as `@import "globals/x"`.
With this fix in place, the node module case can then continue and if no stylesheet is found, the
include paths will then be searched.

(cherry picked from commit d19f260)

Author: clydin

packages/angular_devkit/build_angular/src/builders/browser-esbuild/sass-plugin.ts

@@ -124,7 +124,11 @@ async function compileString(
 
               if (packageResult.path) {
                 return pathToFileURL(
-                  join(dirname(packageResult.path), !hasScope ? nameOrFirstPath : '', ...pathPart),
+                  join(
+                    dirname(packageResult.path),
+                    !hasScope && nameOrFirstPath ? nameOrFirstPath : '',
+                    ...pathPart,
+                  ),
                 );
               }
             }