[arm][arm64] Fix --trace-osr

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}

src/builtins/arm/builtins-arm.cc

@@ -1867,7 +1867,7 @@ void OnStackReplacement(MacroAssembler* masm, OsrSourceTier source,
   {
     Label next;
     __ Move(r1, ExternalReference::address_of_FLAG_trace_osr());
-    __ ldr(r1, MemOperand(r1));
+    __ ldrsb(r1, MemOperand(r1));
     __ tst(r1, Operand(0xFF));  // Mask to the LSB.
     __ b(eq, &next);
 

src/builtins/arm64/builtins-arm64.cc

@@ -2101,7 +2101,7 @@ void OnStackReplacement(MacroAssembler* masm, OsrSourceTier source,
   {
     Label next;
     __ Mov(x1, ExternalReference::address_of_FLAG_trace_osr());
-    __ Ldr(x1, MemOperand(x1));
+    __ Ldrsb(x1, MemOperand(x1));
     __ Tst(x1, 0xFF);  // Mask to the LSB.
     __ B(eq, &next);