[test] Disallow optimisation for baseline flushing tests

Optimisation affects both reachability and tier-up, so disable it for
the flushing tests.

This should de-flake the Numfuzz bots.

Change-Id: I87c479f216eae2d801e7a0dc665e7325bd1b6bd8
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3123415
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: Georg Neis <neis@chromium.org>
Auto-Submit: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Georg Neis <neis@chromium.org>
Cr-Commit-Position: refs/heads/main@{#76526}

test/mjsunit/baseline/flush-baseline-code.js

@@ -5,7 +5,7 @@
 // Flags: --expose-gc --stress-flush-code --allow-natives-syntax
 // Flags: --baseline-batch-compilation-threshold=0 --sparkplug
 // Flags: --no-always-sparkplug --lazy-feedback-allocation
-// Flags: --flush-baseline-code --flush-bytecode
+// Flags: --flush-baseline-code --flush-bytecode --no-opt
 
 function HasBaselineCode(f) {
   let opt_status = %GetOptimizationStatus(f);

test/mjsunit/baseline/flush-only-baseline-code.js

@@ -5,7 +5,7 @@
 // Flags: --expose-gc --stress-flush-code --allow-natives-syntax
 // Flags: --baseline-batch-compilation-threshold=0 --sparkplug
 // Flags: --no-always-sparkplug --lazy-feedback-allocation
-// Flags: --flush-baseline-code --no-flush-bytecode
+// Flags: --flush-baseline-code --no-flush-bytecode --no-opt
 
 function HasBaselineCode(f) {
   let opt_status = %GetOptimizationStatus(f);