Fix util/process test on Cygwin

It seems meson returns the filename with extension for full_path(), even
though Cygwin does it's best to pretend the file doesn't have that
extension.

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4514>

src/util/process_test.c

@@ -75,6 +75,11 @@ test_util_get_process_exec_path (void)
       error = true;
       return;
    }
+#ifdef __CYGWIN__
+   int i = strlen(build_path) - 4;
+   if ((i > 0) && (strcmp(&build_path[i], ".exe") == 0))
+      build_path[i] = 0;
+#endif
    expect_equal_str(build_path, path, "util_get_process_name");
 }