win: taskkill mspdbsrv.exe before updating toolchain

It stays resident, so try to tidy up, otherwise removing the old
directory will fail.

TBR=maruel@chromium.org
BUG=323300

Review URL: https://codereview.chromium.org/140883005

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@245324 0039d316-1c4b-4281-b951-d872f2087c98

win_toolchain/get_toolchain_if_necessary.py

@@ -141,6 +141,8 @@ def main():
   current_hash = CalculateHash(target_dir)
   if current_hash != desired_hash:
     print 'Windows toolchain out of date or doesn\'t exist, updating...'
+    # This stays resident and will make the rmdir below fail.
+    subprocess.call(['taskkill', '/f', '/im', 'mspdbsrv.exe'])
     if os.path.isdir(target_dir):
       subprocess.check_call('rmdir /s/q "%s"' % target_dir, shell=True)
     subprocess.check_call([