llnl.path: make system_path_filter a noop on non-win32 (spack#48032)

Author: haampie

lib/spack/llnl/path.py

@@ -66,7 +66,7 @@ def _is_url(path_or_url: str) -> bool:
     return result
 
 
-def system_path_filter(_func=None, arg_slice: Optional[slice] = None):
+def _system_path_filter(_func=None, arg_slice: Optional[slice] = None):
     """Filters function arguments to account for platform path separators.
     Optional slicing range can be specified to select specific arguments
 
@@ -100,6 +100,16 @@ def path_filter_caller(*args, **kwargs):
     return holder_func
 
 
+def _noop_decorator(_func=None, arg_slice: Optional[slice] = None):
+    return _func if _func else lambda x: x
+
+
+if sys.platform == "win32":
+    system_path_filter = _system_path_filter
+else:
+    system_path_filter = _noop_decorator
+
+
 def sanitize_win_longpath(path: str) -> str:
     """Strip Windows extended path prefix from strings
     Returns sanitized string.