Bug 1797399 - fix rust-analyzer's invocation of mach r=andi

The fix for bug 1759555 involves having rust-analyzer invoke `mach`.
However, `mach` can't be executed directly on Windows systems -- it's a
Python script, not an executable, and so `::CreateProcessW` has no idea
what to do with it.

Work around this by having `mach` explicitly direct `rust-analyzer` to
use `sys.executable` to execute `mach`.

Differential Revision: https://phabricator.services.mozilla.com/D160306

python/mozbuild/mozbuild/backend/mach_commands.py

@@ -8,6 +8,7 @@ import argparse
 import logging
 import os
 import subprocess
+import sys
 
 from mozbuild import build_commands
 
@@ -166,6 +167,7 @@ def setup_vscode(command_context, vscode_cmd):
     clang_tidy_cfg = ClangTidyConfig(command_context.topsrcdir)
 
     cargo_check_command = [
+        sys.executable,
         mozpath.join(command_context.topsrcdir, "mach"),
         "--log-no-times",
         "cargo",