smoketest that libtest doesn't panic in #[bench]

src/test/run-make/test-benches/Makefile

@@ -0,0 +1,9 @@
+include ../../run-make-fulldeps/tools.mk
+
+all:
+	# Smoke-test that `#[bench]` isn't entirely broken.
+	$(RUSTC) --test smokebench.rs -O
+	$(call RUN,smokebench --bench)
+	$(call RUN,smokebench --bench noiter)
+	$(call RUN,smokebench --bench yesiter)
+	$(call RUN,smokebench)

src/test/run-make/test-benches/smokebench.rs

@@ -0,0 +1,14 @@
+#![feature(test)]
+extern crate test;
+
+#[bench]
+fn smoke_yesiter(b: &mut test::Bencher) {
+    let mut i = 0usize;
+    b.iter(|| {
+        i = i.wrapping_add(1);
+        i
+    })
+}
+
+#[bench]
+fn smoke_noiter(_: &mut test::Bencher) {}