PERF: don't recompile css files that have already been compiled

spec/components/discourse_stylesheets_spec.rb

@@ -7,14 +7,14 @@ describe DiscourseStylesheets do
     it "can compile desktop bundle" do
       DiscoursePluginRegistry.stubs(:stylesheets).returns(["#{Rails.root}/spec/fixtures/scss/my_plugin.scss"])
       builder = described_class.new(:desktop)
-      expect(builder.compile).to include('my-plugin-thing')
+      expect(builder.compile(force: true)).to include('my-plugin-thing')
       FileUtils.rm builder.stylesheet_fullpath
     end
 
     it "can compile mobile bundle" do
       DiscoursePluginRegistry.stubs(:mobile_stylesheets).returns(["#{Rails.root}/spec/fixtures/scss/my_plugin.scss"])
       builder = described_class.new(:mobile)
-      expect(builder.compile).to include('my-plugin-thing')
+      expect(builder.compile(force: true)).to include('my-plugin-thing')
       FileUtils.rm builder.stylesheet_fullpath
     end
 
@@ -24,7 +24,7 @@ describe DiscourseStylesheets do
         "#{Rails.root}/spec/fixtures/scss/broken.scss"
       ])
       builder = described_class.new(:desktop)
-      expect(builder.compile).not_to include('my-plugin-thing')
+      expect(builder.compile(force: true)).not_to include('my-plugin-thing')
       FileUtils.rm builder.stylesheet_fullpath
     end
   end