run_single_test: Ensure symlinks exist and are cleaned up

The common test case "268 install functions and follow symlinks"
requires that certain symlinks exist in order to function.

If one clones a fresh repo and executes run_single_test.py with
the aforementioned test as the target it will fail as the required
symlinks are not part of the repo.

Normally these symlinks are created and cleaned up when the
overall testsuite is run but this is not the case for
run_single_test.py

This commit calls the necessary creation and cleanup functions
in the case of run_single_test.py.

run_single_test.py

@@ -16,6 +16,7 @@
 from run_tests import handle_meson_skip_test
 from run_project_tests import TestDef, load_test_json, run_test, BuildStep
 from run_project_tests import setup_commands, detect_system_compiler, detect_tools
+from run_project_tests import setup_symlinks, clear_transitive_files
 
 if T.TYPE_CHECKING:
     from run_project_tests import CompilerArgumentType
@@ -44,6 +45,7 @@ def main() -> None:
     parser.add_argument('--quick', action='store_true', help='Skip some compiler and tool checking')
     args = T.cast('ArgumentType', parser.parse_args())
 
+    setup_symlinks()
     setup_commands(args.backend)
     if not args.quick:
         detect_system_compiler(args)
@@ -95,6 +97,7 @@ def should_fail(path: pathlib.Path) -> str:
                 mlog.log(cmd_res)
             mlog.log(result.stde)
 
+    clear_transitive_files()
     exit(1 if failed else 0)
 
 if __name__ == "__main__":