linux: Fix tests with UBSan
linux: Fix tests with UBSan

Test failures are visible on the clang waterfall here:
https://ci.chromium.org/p/chromium/builders/ci/UBSanVptr%20Linux/49708

R=mentovai@chromium.org

Change-Id: I1627ecb3458721de25861eb915aa269db50ef8ff
Reviewed-on: https://chromium-review.googlesource.com/c/crashpad/crashpad/+/2466367
Reviewed-by: Mark Mentovai <f1b5a91d4d6ad523f2610114591c007e75d15084@chromium.org>

chromium/crashpad,chromium/crashpad,chromium/crashpad