Add and update rustdoc ui test

src/test/rustdoc-ui/cfg-test.stdout

@@ -1,6 +1,7 @@
 
-running 1 test
+running 2 tests
+test $DIR/cfg-test.rs - Bar (line 28) ... ok
 test $DIR/cfg-test.rs - Foo (line 20) ... ok
 
-test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out
+test result: ok. 2 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out
 

src/test/rustdoc-ui/doc-test-doctest-feature.rs

@@ -0,0 +1,15 @@
+// build-pass
+// compile-flags:--test
+// normalize-stdout-test: "src/test/rustdoc-ui" -> "$$DIR"
+
+#![feature(cfg_doctest)]
+
+// Make sure `cfg(doctest)` is set when finding doctests but not inside
+// the doctests.
+
+/// ```
+/// #![feature(cfg_doctest)]
+/// assert!(!cfg!(doctest));
+/// ```
+#[cfg(doctest)]
+pub struct Foo;

src/test/rustdoc-ui/doc-test-doctest-feature.stdout

@@ -0,0 +1,6 @@
+
+running 1 test
+test $DIR/doc-test-doctest-feature.rs - Foo (line 10) ... ok
+
+test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out
+