Add a run-make test for non-cross --print=target-cpus

Author: Zalathar

tests/run-make/print-target-cpus-native/rmake.rs

@@ -0,0 +1,23 @@
+//@ ignore-cross-compile ("native" is only printed when host==target)
+
+use run_make_support::{assert_contains_regex, rfs, rustc, target};
+
+// Test that the first CPU printed by `--print=target-cpus` for the non-cross
+// target is "native", with a suitable remark.
+
+fn main() {
+    let expected = r"^Available CPUs for this target:
+    native +- Select the CPU of the current host \(currently [^ )]+\)\.
+";
+
+    // Without an explicit target.
+    rustc().print("target-cpus").run().assert_stdout_contains_regex(expected);
+
+    // With an explicit target that happens to be the host.
+    let host = target(); // Because of ignore-cross-compile, assume host == target.
+    rustc().print("target-cpus").target(host).run().assert_stdout_contains_regex(expected);
+
+    // With an explicit output path.
+    rustc().print("target-cpus=./xyzzy.txt").run().assert_stdout_equals("");
+    assert_contains_regex(rfs::read_to_string("./xyzzy.txt"), expected);
+}