fix --free-up-disk action on windows

Summary:
X-link: facebook/watchman#1314

on windows git checkout sets some files in readonly mode, which can block the free up disk action.

Add a variant of rmtree that checks for this and clears the readonly flag

e.g. failure in https://github.com/facebook/watchman/actions/runs/19267503560/job/55086850056
```
  File "C:\hostedtoolcache\windows\Python\3.9.13\x64\lib\shutil.py", line 629, in _rmtree_unsafe
    onerror(os.unlink, fullname, sys.exc_info())
  File "C:\hostedtoolcache\windows\Python\3.9.13\x64\lib\shutil.py", line 627, in _rmtree_unsafe
    os.unlink(fullname)
PermissionError: [WinError 5] Access is denied: 'Z:\build\fbthrift\source\.git\objects\pack\pack-1e9bd81db474c833f5ee1eec341f0ae8f4c05a51.idx'
```

Reviewed By: bigfootjon

Differential Revision: D86773115

fbshipit-source-id: f665d43fb70dfe6ee1a8dc596f8cd09ac8a5bf7f

Author: ahornby

build/fbcode_builder/getdeps/builder.py

@@ -18,7 +18,7 @@
 from shlex import quote as shellquote
 from typing import Optional
 
-from .copytree import simple_copytree
+from .copytree import rmtree_more, simple_copytree
 from .dyndeps import create_dyn_dep_munger
 from .envfuncs import add_path_entry, Env, path_search
 from .fetcher import copy_if_different, is_public_commit
@@ -203,7 +203,7 @@ def build(self, reconfigure: bool) -> None:
                 if os.path.islink(self.build_dir):
                     os.remove(self.build_dir)
                 else:
-                    shutil.rmtree(self.build_dir)
+                    rmtree_more(self.build_dir)
         elif self.build_opts.is_windows():
             # On Windows, emit a wrapper script that can be used to run build artifacts
             # directly from the build directory, without installing them.  On Windows $PATH

build/fbcode_builder/getdeps/copytree.py

@@ -7,6 +7,7 @@
 
 import os
 import shutil
+import stat
 import subprocess
 
 from .platform import is_windows
@@ -97,3 +98,31 @@ def simple_copytree(src_dir, dest_dir, symlinks=False):
         return dest_dir
     else:
         return shutil.copytree(src_dir, dest_dir, symlinks=symlinks)
+
+
+def _remove_readonly_and_try_again(func, path, exc_info):
+    """
+    Error handler for shutil.rmtree.
+    If the error is due to an access error (read only file)
+    it attempts to add write permission and then retries the operation.
+    Any other failure propagates.
+    """
+    # exc_info is a tuple (exc_type, exc_value, traceback)
+    exc_type = exc_info[0]
+    if exc_type is PermissionError:
+        os.chmod(path, stat.S_IWRITE)
+        # Retry the original function (os.remove or os.rmdir)
+        try:
+            func(path)
+        except Exception:
+            # If it still fails, the original exception from func() will propagate
+            raise
+    else:
+        # If the error is not a PermissionError, re-raise the original exception
+        raise exc_info[1]
+
+
+def rmtree_more(path):
+    """Wrapper around shutil.rmtree() that makes it remove readonly files as well.
+    Useful when git on windows decides to make some files readonly on checkout"""
+    shutil.rmtree(path, onerror=_remove_readonly_and_try_again)