Fix tests/run.py handling of existing build directory

tests/run.py

@@ -121,24 +121,29 @@ def create_test_workdir(
     test_workdir: Path,
     custom_gdextension_api: Optional[Path],
 ) -> None:
-    if test_workdir.exists():
+    try:
+        # Check the directory exists and is not empty
+        next(test_workdir.iterdir())
         print(
             f"{YELLOW}{test_dir.name}: workdir {test_workdir} already populated, leaving it as is{NO_COLOR}",
             flush=True,
         )
+        return
+    except (FileNotFoundError, StopIteration):
+        pass
+
+    print(
+        f"{YELLOW}{test_dir.name}: Create&populate test workdir in {test_workdir}{NO_COLOR}",
+        flush=True,
+    )
+    shutil.copytree(test_dir, test_workdir, dirs_exist_ok=True, symlinks=True)
+    symlink(distrib_workdir / "addons", test_workdir / "addons")
+    shutil.copy(distrib_workdir / "pythonscript.gdextension", test_workdir)
+    # GDExtension headers are needed to compile Cython modules
+    if custom_gdextension_api:
+        shutil.copytree(custom_gdextension_api, test_workdir / "gdextension_api", symlinks=True)
     else:
-        print(
-            f"{YELLOW}{test_dir.name}: Create&populate test workdir in {test_workdir}{NO_COLOR}",
-            flush=True,
-        )
-        shutil.copytree(test_dir, test_workdir, dirs_exist_ok=True, symlinks=True)
-        symlink(distrib_workdir / "addons", test_workdir / "addons")
-        shutil.copy(distrib_workdir / "pythonscript.gdextension", test_workdir)
-        # GDExtension headers are needed to compile Cython modules
-        if custom_gdextension_api:
-            shutil.copytree(custom_gdextension_api, test_workdir / "gdextension_api", symlinks=True)
-        else:
-            symlink(build_dir / "gdextension_api", test_workdir / "gdextension_api")
+        symlink(build_dir / "gdextension_api", test_workdir / "gdextension_api")
 
     build_script = test_workdir / "build.py"
     if build_script.exists():