Pass --no-junction flag to depot_tools script for windows toolchain

This cancels the effect of https://source.chromium.org/chromium/chromium/tools/depot_tools/+/c6684fda9877962580c021aab7c8bc0e9f1c2647.

Change-Id: If8a46bbcc1d1d8b645609d3a9d6f174e3d420edd
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/419841
Reviewed-by: Alexander Thomas <[email protected]>
Commit-Queue: Ivan Inozemtsev <[email protected]>

Author: iinozemtsev

build/vs_toolchain.py

@@ -528,6 +528,7 @@ def Update(force=False, no_download=False):
                     'get_toolchain_if_necessary.py'),
         '--output-json', json_data_file,
         '--toolchain-dir', toolchain_dir,
+        '--no-junction',
       ] + _GetDesiredVsToolchainHashes()
     if force:
       get_toolchain_args.append('--force')