Add test for --no-source option flag

Author: GuillaumeGomez

src/test/rustdoc/html_no_source_attr.rs

@@ -0,0 +1,6 @@
+#![doc(html_no_source)]
+#![crate_name = "foo"]
+
+// @!has src/foo/html_no_source_attr.rs.html
+// @has foo/index.html
+// @!has - '//*[@class="srclink"]' '[src]'

src/test/rustdoc/html_no_source_flag.rs

@@ -0,0 +1,7 @@
+// compile-flags: --no-source
+
+#![crate_name = "foo"]
+
+// @!has src/foo/html_no_source_attr.rs.html
+// @has foo/index.html
+// @!has - '//*[@class="srclink"]' '[src]'

src/test/rustdoc/html_source.rs

@@ -0,0 +1,5 @@
+#![crate_name = "foo"]
+
+// @has src/foo/html_source.rs.html
+// @has foo/index.html
+// @has - '//*[@class="srclink"]' '[src]'