Add test for ordering of examples, simplify with single scrape.mk file

src/test/run-make/rustdoc-scrape-examples-ordering/examples/ex1.rs

@@ -0,0 +1,9 @@
+fn main() {
+    foobar::ok();
+
+    // this is a
+
+    // BIG
+
+    // item
+}