Attempt to avoid VCVARSALL.BAT breakage entirely.

Change-Id: I9b4b4e64f463e5b55fbc9c22e12b7d3e7fecc172
Reviewed-on: https://code-review.googlesource.com/c/re2/+/44222
Reviewed-by: Paul Wankadia <junyer@google.com>
1 file changed