[test] Disallow BG compile stress in log test

The log test checks for log positions, which may change when background
serialization / background compilation are enabled.

Fixed: v8:12117
Change-Id: I193c9c23e016fad1e3f06a9f377bb53db84a6988
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3129421
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Auto-Submit: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/main@{#76573}

test/mjsunit/tools/log_two_byte.js

@@ -3,6 +3,7 @@
 // found in the LICENSE file.
 
 // Flags: --logfile='+' --log --log-code --log-function-events --no-stress-opt
+// Flags: --no-stress-background-compile
 
 let twoByteName = "twoByteName_🍕"
 let o = {