fix(@schematics/angular): use join for sourceRoot

It was using '/src' for the base new project.

Author: filipesilva

packages/schematics/angular/application/index.ts

@@ -137,7 +137,7 @@ function addAppToWorkspaceFile(options: ApplicationOptions, workspace: Workspace
 
   const project: WorkspaceProject = {
     root: projectRoot,
-    sourceRoot: `${projectRoot}/src`,
+    sourceRoot: join(normalize(projectRoot), 'src'),
     projectType: 'application',
     prefix: options.prefix || 'app',
     schematics,