test: add locale-aware decimal separator test for sort -g

Add test to verify that sort's general numeric (-g) option correctly handles
decimal separators based on locale settings, ensuring proper ordering of
numbers like "1,9" vs "1,10" in French locale (comma as separator).

Author: mattsu2020

tests/by-util/test_sort.rs

@@ -1559,6 +1559,32 @@ fn test_g_float() {
         .stdout_is(output);
 }
 
+#[test]
+fn test_g_float_locale_decimal_separator() {
+    let Ok(locale_fr_utf8) = env::var("LOCALE_FR_UTF8") else {
+        return;
+    };
+    if locale_fr_utf8 == "none" {
+        return;
+    }
+
+    let ts = TestScenario::new("sort");
+
+    ts.ucmd()
+        .env("LC_ALL", &locale_fr_utf8)
+        .args(&["-g", "--stable"])
+        .pipe_in("1,9\n1,10\n")
+        .succeeds()
+        .stdout_is("1,10\n1,9\n");
+
+    ts.ucmd()
+        .env("LC_ALL", &locale_fr_utf8)
+        .args(&["-g", "--stable"])
+        .pipe_in("1.9\n1.10\n")
+        .succeeds()
+        .stdout_is("1.10\n1.9\n");
+}
+
 #[test]
 // Test misc numbers ("'a" is not interpreted as literal, trailing text is ignored...)
 fn test_g_misc() {