Currently, `intl/regress-7770` fails on environments with `LC_ALL`
set, e.g.

    export LC_ALL=en_US.UTF-8

While engineers can manually work around it using `unset LC_ALL`
before running the test suite, it would be more convenient if the test
runner didn't rely on the absence of this environment variable in the
first place.

Bug: v8:8845
Change-Id: I8116e2fd369be1d561dfe465f2901d07d3f75510
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1680538
Commit-Queue: Mathias Bynens <mathias@chromium.org>
Commit-Queue: Tamer Tas <tmrts@chromium.org>
Auto-Submit: Mathias Bynens <mathias@chromium.org>
Reviewed-by: Tamer Tas <tmrts@chromium.org>
Cr-Commit-Position: refs/heads/master@{#62417}