Read only a single byte of FLAG_trace_osr in assembly builtin code to
make asan happy in the simulator.

Bug: chromium:1324042
Change-Id: I002cea0b4917af3780d6bdedfb0ec55008e146c7
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3644793Reviewed-by: Shu-yu Guo <syg@chromium.org>
Commit-Queue: Shu-yu Guo <syg@chromium.org>
Auto-Submit: Camillo Bruni <cbruni@chromium.org>
Cr-Commit-Position: refs/heads/main@{#80532}