fix: fail tests when make-change fails

It fails now, because it doesn't exist.

ofborg/src/tasks/build.rs

@@ -427,14 +427,18 @@ mod tests {
     }
 
     fn make_pr_repo(bare: &Path, co: &Path) -> String {
-        let output = Command::new("bash")
-            .current_dir(tpath("./test-srcs"))
+        let mut cmd = Command::new("bash");
+
+        cmd.current_dir(tpath("./test-srcs"))
             .arg("make-change.sh")
             .arg(bare)
             .arg(co)
             .stderr(Stdio::null())
-            .stdout(Stdio::piped())
-            .output()
+            .stdout(Stdio::piped());
+
+        assert!(cmd.status().unwrap().success());
+
+        let output = cmd.output()
             .expect("building the test PR failed");
         let hash = String::from_utf8(output.stdout).expect("Should just be a hash");