uutests: preserve PATH in UCommand to fix NixOS test failures

This ensures that the PATH environment variable is preserved even when cleared, allowing tests to find system utilities on NixOS where they are not in standard locations like /bin.

Fixes #10756

tests/uutests/src/lib/util.rs

@@ -1823,6 +1823,12 @@ impl UCommand {
         }
 
         command.env_clear();
+
+        // Preserve PATH
+        if let Some(path) = env::var_os("PATH") {
+            command.env("PATH", path);
+        }
+
         if cfg!(windows) {
             // spell-checker:ignore (dll) rsaenh
             // %SYSTEMROOT% is required on Windows to initialize crypto provider