hopefully make the tests work on win32

cc-test/build.rs

@@ -124,7 +124,7 @@ fn main() {
 fn run_forked_capture_output(out: &Path, action: &str) {
     let program = env::current_exe().unwrap();
     let output = Command::new(&program).arg(action).output().unwrap();
-    assert!(output.status.success());
+    assert!(output.status.success(), "output: {:#?}", output);
     // we've captured the output and now we write it to a dedicated directory in the
     // build output so our tests can access the output.
     let action_dir = out.join(action);
@@ -152,10 +152,9 @@ fn build_cargo_warnings(warnings: bool) {
     cc::Build::new()
         .cargo_metadata(false)
         .cargo_warnings(warnings)
-        .file("src/compile_error.c")
-        .try_compile("compile_error")
-        // we expect the compilation to fail in this case
-        .unwrap_err();
+        .file("src/compile_warning.c")
+        .try_compile("compile_warning")
+        .unwrap();
 }
 
 fn build_cargo_metadata(metadata: bool) {

cc-test/src/compile_warning.c

@@ -0,0 +1,3 @@
+#warning "if you see this, cargo_warnings(false) didn't do its job"
+
+void compile_warning(void) {}

cc-test/src/dummy.c

@@ -1 +1,3 @@
 /* just an empty file */
+
+void dummy(void) {}

cc-test/tests/output.rs

@@ -19,16 +19,35 @@ fn cargo_warnings_off() {
 fn cargo_metadata_on() {
     let (stdout, stderr) = load_output("metadata-on");
     assert!(stderr.is_empty());
-    assert!(stdout.contains("rustc-link-lib="));
-    assert!(stdout.contains("rustc-link-search="));
+    assert!(stdout.contains("cargo:rustc-link-lib="));
+    assert!(stdout.contains("cargo:rustc-link-search="));
 }
 
 #[test]
 fn cargo_metadata_off() {
     let (stdout, stderr) = load_output("metadata-off");
     assert!(stderr.is_empty());
-    assert!(!stdout.contains("rustc-link-lib="));
-    assert!(!stdout.contains("rustc-link-search="));
+
+    // most of the instructions aren't currently used
+    const INSTRUCTIONS: &[&str] = &[
+        "cargo:rerun-if-changed=",
+        "cargo:rerun-if-env-changed=",
+        "cargo:rustc-cdylib-link-arg=",
+        "cargo:rustc-cfg=",
+        "cargo:rustc-env=",
+        "cargo:rustc-flags=",
+        "cargo:rustc-link-arg-benches=",
+        "cargo:rustc-link-arg-bin=",
+        "cargo:rustc-link-arg-bins=",
+        "cargo:rustc-link-arg-examples=",
+        "cargo:rustc-link-arg-tests=",
+        "cargo:rustc-link-arg=",
+        "cargo:rustc-link-lib=",
+        "cargo:rustc-link-search=",
+    ];
+    for instr in INSTRUCTIONS {
+        assert!(!stdout.contains(instr), "instruction present: {}", instr);
+    }
 }
 
 #[track_caller]