install: don't panic when the strip program is killed by a signal (#12730)

`install -s --strip-program=PROG` aborted with an Option::unwrap panic when
PROG was terminated by a signal: the strip-failure branch formatted its error
with `status.code().unwrap()`, but `ExitStatus::code()` is `None` for a
signal-terminated process.

Branch on `status.code()`: keep the existing "exit code: N" message for a
normal non-zero exit, and use a new `install-error-strip-terminated` message
("strip process terminated abnormally") for the signal case — matching GNU,
which reports the same and exits 1. Adds the locale key to en-US and fr-FR and
a regression test.

src/uu/install/locales/en-US.ftl

@@ -33,6 +33,7 @@ install-error-backup-failed = cannot backup { $from } to { $to }
 install-error-install-failed = cannot install { $from } to { $to }: { $error }
 install-error-strip-failed = strip program failed: { $error }
 install-error-strip-abnormal = strip process terminated abnormally - exit code: { $code }
+install-error-strip-terminated = strip process terminated abnormally
 install-error-metadata-failed = metadata error
 install-error-invalid-user = invalid user: { $user }
 install-error-invalid-group = invalid group: { $group }

src/uu/install/locales/fr-FR.ftl

@@ -33,6 +33,7 @@ install-error-backup-failed = impossible de sauvegarder { $from } vers { $to }
 install-error-install-failed = impossible d'installer { $from } vers { $to }: { $error }
 install-error-strip-failed = échec du programme strip : { $error }
 install-error-strip-abnormal = le processus strip s'est terminé anormalement - code de sortie : { $code }
+install-error-strip-terminated = le processus strip s'est terminé anormalement
 install-error-metadata-failed = erreur de métadonnées
 install-error-invalid-user = utilisateur invalide : { $user }
 install-error-invalid-group = groupe invalide : { $group }

src/uu/install/src/install.rs

@@ -97,6 +97,9 @@ enum InstallError {
     #[error("{}", translate!("install-error-strip-failed", "error" => .0.clone()))]
     StripProgramFailed(String),
 
+    #[error("{}", translate!("install-error-strip-terminated"))]
+    StripTerminated,
+
     #[error("{}", translate!("install-error-metadata-failed"))]
     MetadataFailed(#[source] std::io::Error),
 
@@ -1024,9 +1027,14 @@ fn strip_file(to: &Path, b: &Behavior) -> UResult<()> {
             if !status.success() {
                 // Follow GNU's behavior: if strip fails, removes the target
                 let _ = fs::remove_file(to);
-                return Err(InstallError::StripProgramFailed(
-                    translate!("install-error-strip-abnormal", "code" => status.code().unwrap()),
-                )
+                // A signal-terminated strip has no exit code; report GNU's
+                // "strip process terminated abnormally" instead of unwrapping None.
+                return Err(match status.code() {
+                    Some(code) => InstallError::StripProgramFailed(
+                        translate!("install-error-strip-abnormal", "code" => code),
+                    ),
+                    None => InstallError::StripTerminated,
+                }
                 .into());
             }
         }

tests/by-util/test_install.rs

@@ -935,6 +935,26 @@ fn test_install_and_strip_with_invalid_program() {
     assert!(!at.file_exists(STRIP_TARGET_FILE));
 }
 
+#[test]
+#[cfg(not(windows))]
+fn test_install_and_strip_with_signal_terminated_program() {
+    let scene = TestScenario::new(util_name!());
+    let at = &scene.fixtures;
+    at.write("src.sh", "kill -9 $$\n");
+    scene
+        .ucmd()
+        .args(&[
+            "-s",
+            "--strip-program",
+            "/bin/sh",
+            "src.sh",
+            STRIP_TARGET_FILE,
+        ])
+        .fails()
+        .stderr_only("install: strip process terminated abnormally\n");
+    assert!(!at.file_exists(STRIP_TARGET_FILE));
+}
+
 #[test]
 #[cfg(not(windows))]
 fn test_install_and_strip_with_non_existent_program() {