When building with GCC8.1, has error: variable ‘kUpperBoundIsMax’,
‘kLowerBoundIsMin’ set but not used [-Werror=unused-but-set-variable]
so, using USE(var) to fix this error

Change-Id: I05133d3cb5843f4c0a4a59591470b0fcaa21f16f
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1848852
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Reviewed-by: Clemens Backes <clemensb@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#64245}