Don't create unneeded _build dir at top-level.

dev-tools/dev_tools.py

@@ -241,8 +241,6 @@ def _run_apidoc():
 
 
 def _run_sphinx_build():
-    _ensure_empty_local_dir_exists("_build")
-
     cmd = [
         f"{_SCRIPTS_DIR / 'sphinx-build'}",
         "-M",
@@ -254,16 +252,6 @@ def _run_sphinx_build():
     _print_and_run(cmd)
 
 
-def _ensure_empty_local_dir_exists(dir_name):
-    dir_path = pl.Path(dir_name)
-
-    if dir_path.is_dir():
-        sh.rmtree(dir_path)
-        time.sleep(1)
-
-    dir_path.mkdir()
-
-
 def _print_and_run(args: tp.Sequence[str]) -> None:
     formatted_args = " ".join(str(arg) for arg in args)
     print(f"Running '{formatted_args}'...")