speed up file copy on windows

Summary:
getdeps windows file copy is very slow, speed it up

Test Plan:

Fetch
```
rm -rf z:/installed/perl-* # z:/build/perl-* z:/extracted/perl-*
time python ./build/fbcode_builder/getdeps.py fetch perl
```

Before, 40s:
```
Building on {distro=None, distro_vers=10, fb=off, fbsource=off, os=windows, shared_libs=off, test=on}
Assessing perl...
Installing Z:\extracted\perl-strawberry-perl-5.28.1.1-64bit-portable.zip\perl -> Z:\installed\perl-DRGAS42y_YT9hZddELBr4c7ZE50hkZy1Cybn7PLzwFc

real    0m40.150s
user    0m0.000s
sys     0m0.000s
```

After:
```
$ rm -rf z:/installed/perl-*
04 Dec 2024 19:55:39
04 Dec 2024 19:55:39 [Exit: 0] alex@fridge:~/local/folly
$ time python ./build/fbcode_builder/getdeps.py build perl
04 Dec 2024 19:55:42
Building on {distro=None, distro_vers=10, fb=off, fbsource=off, os=windows, shared_libs=off, test=on}
Assessing perl...
Installing Z:\extracted\perl-strawberry-perl-5.28.1.1-64bit-portable.zip\perl -> Z:\installed\perl-DRGAS42y_YT9hZddELBr4c7ZE50hkZy1Cybn7PLzwFc
---
+ robocopy.exe \
+      'Z:\extracted\perl-strawberry-perl-5.28.1.1-64bit-portable.zip\perl' \
+      'Z:\installed\perl-DRGAS42y_YT9hZddELBr4c7ZE50hkZy1Cybn7PLzwFc' \
+      /E \
+      /NFL \
+      /NDL \
+      /NJH \
+      /NJS \
+      NP


real    0m0.758s
user    0m0.000s
sys     0m0.000s
04 Dec 2024 19:55:43 [Exit: 0] alex@fridge:~/local/folly
```

build/fbcode_builder/getdeps/builder.py

@@ -18,6 +18,7 @@
 from shlex import quote as shellquote
 from typing import Optional
 
+from .copytree import simple_copytree
 from .dyndeps import create_dyn_dep_munger
 from .envfuncs import add_path_entry, Env, path_search
 from .fetcher import copy_if_different
@@ -1327,7 +1328,7 @@ def build(self, reconfigure: bool) -> None:
                     os.makedirs(dest_parent)
                 if os.path.isdir(full_src):
                     if not os.path.exists(full_dest):
-                        shutil.copytree(full_src, full_dest)
+                        simple_copytree(full_src, full_dest)
                 else:
                     shutil.copyfile(full_src, full_dest)
                     shutil.copymode(full_src, full_dest)
@@ -1339,7 +1340,7 @@ def build(self, reconfigure: bool) -> None:
                         os.chmod(full_dest, st.st_mode | stat.S_IXUSR)
         else:
             if not os.path.exists(self.inst_dir):
-                shutil.copytree(self.src_dir, self.inst_dir)
+                simple_copytree(self.src_dir, self.inst_dir)
 
 
 class SqliteBuilder(BuilderBase):

build/fbcode_builder/getdeps/copytree.py

@@ -10,6 +10,7 @@
 import subprocess
 
 from .platform import is_windows
+from .runcmd import run_cmd
 
 
 PREFETCHED_DIRS = set()
@@ -64,7 +65,6 @@ def prefetch_dir_if_eden(dirpath) -> None:
     subprocess.call(["edenfsctl", "prefetch", "--repo", root, glob, "--background"])
     PREFETCHED_DIRS.add(dirpath)
 
-
 # pyre-fixme[9]: ignore has type `bool`; used as `None`.
 def copytree(src_dir, dest_dir, ignore: bool = None):
     """Recursively copy the src_dir to the dest_dir, filtering
@@ -80,3 +80,25 @@ def copytree(src_dir, dest_dir, ignore: bool = None):
     #  `Union[typing.Callable[[Union[PathLike[str], str], List[str]], Iterable[str]],
     #  typing.Callable[[str, List[str]], Iterable[str]], None]` but got `bool`.
     return shutil.copytree(src_dir, dest_dir, ignore=ignore)
+
+def simple_copytree(src_dir, dest_dir,  symlinks=False):
+    """A simple version of shutil.copytree() that can delegate to native tools when its faster"""
+    if is_windows():
+        os.makedirs(dest_dir, exist_ok=True)
+        args = [
+            src_dir, dest_dir, 
+            # copy directories, including empty ones
+            "/E", 
+            # Ignore Extra files in destination
+            "/XX",
+            # enable parallel copy
+            "/MT:",
+            # be quiet
+            "/NFL", "/NDL", "/NJH", "/NJS", "/NP",
+        ]
+        if symlinks:
+            args.append("/SL")
+        run_cmd(["robocopy.exe"] + args)
+        return dest_dir
+    else:
+        return shutil.copytree(src_dir, dest_dir, symlinks=symlinks)