fix(test): stop executable fixtures racing ETXTBSY under parallel tests

src/rust/provers/test_fixture.rs

@@ -15,7 +15,7 @@
 //! once on any argument they do not expect, so the probe runs no fixture body.
 
 use std::io::{ErrorKind, Write};
-use std::os::unix::fs::OpenOptionsExt;
+use std::os::unix::fs::{OpenOptionsExt, PermissionsExt};
 use std::path::Path;
 use std::time::Duration;
 
@@ -29,10 +29,14 @@
             .create_new(true)
             .mode(0o700)
             .open(path)
             .expect("create fixture executable");
         file.write_all(contents.as_bytes())
             .expect("write fixture executable");
     }
+    // The creation mode is filtered by the umask; set it explicitly so the
+    // fixture is executable whatever umask the test runner inherited.
+    std::fs::set_permissions(path, std::fs::Permissions::from_mode(0o700))
+        .expect("make fixture executable");
     for _ in 0..200 {
         match std::process::Command::new(path)
             .arg("--echidna-fixture-ready")
@@ -44,7 +48,7 @@
             Err(error) if error.kind() == ErrorKind::ExecutableFileBusy => {
                 std::thread::sleep(Duration::from_millis(10));
             },
             Err(error) => panic!("fixture executable cannot run: {error}"),
             Ok(_) => return,
         }
     }