Add test for rustdoc --nocapture option

Author: GuillaumeGomez

src/test/rustdoc-ui/nocapture.rs

@@ -0,0 +1,10 @@
+// check-pass
+// compile-flags:--test -Zunstable-options --nocapture
+// normalize-stdout-test: "src/test/rustdoc-ui" -> "$$DIR"
+// normalize-stdout-test "finished in \d+\.\d+s" -> "finished in $$TIME"
+
+/// ```
+/// println!("hello!");
+/// eprintln!("stderr");
+/// ```
+pub struct Foo;

src/test/rustdoc-ui/nocapture.stderr

@@ -0,0 +1 @@
+stderr

src/test/rustdoc-ui/nocapture.stdout

@@ -0,0 +1,7 @@
+
+running 1 test
+hello!
+test $DIR/nocapture.rs - Foo (line 6) ... ok
+
+test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in $TIME
+