MSAN currently detects false positives on global/static
thread_local variables which are created at library load
time. This CL mutes the false positive in order to unblock
running blink_web_tests with SwANGLE on MSAN bots.

Bug: chromium:1211047
Change-Id: I7cd103d470177d783df7f73ca6ceeedc0774b163
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2920486
Commit-Queue: Alexis Hétu <sugoi@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>