Get BTD tests to at least run buck on Windows

Summary:
Before, the tests would fail with something like:

    ...
    popenargs = (('C:\\open\\fbsource\\buck-out\\v2\\gen\\fbcode\\594a1ac7617488da\\target_determinator\\targets\\__targets__\\targets..._determinator\\btd\\test\\run_buck.sh', '--output', WindowsPath('C:/cygwin/tmp/tmplc5a47wa/base.jsonl'), 'root//...'),)
    kwargs = {'encoding': 'utf-8', 'stderr': -1, 'stdout': -1}
    process = <Popen: returncode: 1 args: ('C:\\open\\fbsource\\buck-out\\v2\\gen\\fbcode\...>
    stdout = ''
    stderr = 'Error: Other(%1 is not a valid Win32 application. (os error 193))\n'
    retcode = 1
    ...

But now they fail with an actual problem in the test or code.

Reviewed By: rjbailey

Differential Revision: D65670273

fbshipit-source-id: aa5c8afda0502101bc680cc4b750241593bad9c7

btd/test/run_buck.bat

@@ -0,0 +1,8 @@
+@REM Copyright (c) Meta Platforms, Inc. and affiliates.
+@REM
+@REM This source code is licensed under both the MIT license found in the
+@REM LICENSE-MIT file in the root directory of this source tree and the Apache
+@REM License, Version 2.0 found in the LICENSE-APACHE file in the root directory
+@REM of this source tree.
+
+@dotslash "%BUCK2%" --no-buckd --isolation-dir=btd_testing %*