autotools: Fix config.guess detection (#17149)

The config.guess detection used a relative path that did not work in
combination with `check_call`. Use an absolute path instead.

lib/spack/spack/build_systems/autotools.py

@@ -118,13 +118,15 @@ def _do_patch_config_files(self):
             config_file = 'config.{0}'.format(config_name)
             if os.path.exists(config_file):
                 # First search the top-level source directory
-                my_config_files[config_name] = config_file
+                my_config_files[config_name] = os.path.join(
+                    self.configure_directory, config_file)
             else:
                 # Then search in all sub directories recursively.
                 # We would like to use AC_CONFIG_AUX_DIR, but not all packages
                 # ship with their configure.in or configure.ac.
                 config_path = next((os.path.join(r, f)
-                                    for r, ds, fs in os.walk('.') for f in fs
+                                    for r, ds, fs in os.walk(
+                                        self.configure_directory) for f in fs
                                     if f == config_file), None)
                 my_config_files[config_name] = config_path