When doing VS 2017 official builds of some targets, including
mksnapshot.exe, a warning about a buffer overrun is shown. After
analysis and discussion with Microsoft it was decided that this warning
is spurious. The warning is:

    warning C4789: buffer 'key' of size 16 bytes will be overrun; 4
    bytes will be written starting at offset 16

Despite the certain language "4 bytes *will* be written..." it is in
fact a heuristic based warning. Suppressing it at this point in the
inlining stack appears to avoid the issues.

R=hablich@chromium.org
BUG=v8:6068

Review-Url: https://codereview.chromium.org/2804033005
Cr-Commit-Position: refs/heads/master@{#44625}