microbenchmarks: update to _FORTIFY_SOURCE=3 Since this project explicitly specifies its FORTIFY level, update it to the level CrOS wants to move to. This isn't _removed_, since it's copied from a template file, and consistency with that seems useful. BUG=b:288411201 TEST=CQ+1 Change-Id: I38321ba9cc61f756907b62b519542f5f070791ae Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/microbenchmarks/+/4707192 Reviewed-by: Vovo Yang <[email protected]> Tested-by: George Burgess <[email protected]> Commit-Queue: George Burgess <[email protected]>