Reland "[flag] Disable W^X behind --future"

This is a reland of b06f3832

s/DEFINE_READONLY_BOOL/DEFINE_BOOL_READONLY/

Original change's description:
> [flag] Disable W^X behind --future
>
> Measure the impact of W^X on --future bots
>
> Change-Id: I6f60cc835471fa62ec0871101eca5d3022ece519
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3168277
> Commit-Queue: Leszek Swirski <leszeks@chromium.org>
> Auto-Submit: Leszek Swirski <leszeks@chromium.org>
> Reviewed-by: Toon Verwaest <verwaest@chromium.org>
> Reviewed-by: Hannes Payer <hpayer@chromium.org>
> Cr-Commit-Position: refs/heads/main@{#76908}

Cq-Include-Trybots: luci.v8.try:v8_mac_arm64_dbg_ng,v8_mac_arm64_compile_dbg
Change-Id: Iae6da3a64d19d3c03d565cc94f765bc41e36bfb1
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3168620
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Cr-Commit-Position: refs/heads/main@{#76916}

src/flags/flag-definitions.h

@@ -211,6 +211,13 @@ struct MaybeBoolFlag {
 #define ENABLE_SPARKPLUG_BY_DEFAULT false
 #endif
 
+#if defined(V8_OS_MACOSX) && defined(V8_HOST_ARCH_ARM64)
+// Must be enabled on M1.
+#define MUST_WRITE_PROTECT_CODE_MEMORY true
+#else
+#define MUST_WRITE_PROTECT_CODE_MEMORY false
+#endif
+
 // Supported ARM configurations are:
 //  "armv6":       ARMv6 + VFPv2
 //  "armv7":       ARMv7 + VFPv3-D32 + NEON
@@ -509,6 +516,9 @@ DEFINE_WEAK_IMPLICATION(future, flush_baseline_code)
 #if V8_SHORT_BUILTIN_CALLS
 DEFINE_WEAK_IMPLICATION(future, short_builtin_calls)
 #endif
+#if !MUST_WRITE_PROTECT_CODE_MEMORY
+DEFINE_WEAK_VALUE_IMPLICATION(future, write_protect_code_memory, false)
+#endif
 
 // Flags for jitless
 DEFINE_BOOL(jitless, V8_LITE_BOOL,
@@ -1180,7 +1190,12 @@ DEFINE_INT(scavenge_task_trigger, 80,
 DEFINE_BOOL(scavenge_separate_stack_scanning, false,
             "use a separate phase for stack scanning in scavenge")
 DEFINE_BOOL(trace_parallel_scavenge, false, "trace parallel scavenge")
+#if MUST_WRITE_PROTECT_CODE_MEMORY
+DEFINE_BOOL_READONLY(write_protect_code_memory, true,
+                     "write protect code memory")
+#else
 DEFINE_BOOL(write_protect_code_memory, true, "write protect code memory")
+#endif
 #if defined(V8_ATOMIC_MARKING_STATE) && defined(V8_ATOMIC_OBJECT_FIELD_WRITES)
 #define V8_CONCURRENT_MARKING_BOOL true
 #else
@@ -1983,7 +1998,9 @@ DEFINE_PERF_PROF_BOOL(
     "Remove the perf file right after creating it (for testing only).")
 DEFINE_NEG_IMPLICATION(perf_prof, compact_code_space)
 // TODO(v8:8462) Remove implication once perf supports remapping.
+#if !MUST_WRITE_PROTECT_CODE_MEMORY
 DEFINE_NEG_IMPLICATION(perf_prof, write_protect_code_memory)
+#endif
 #if V8_ENABLE_WEBASSEMBLY
 DEFINE_NEG_IMPLICATION(perf_prof, wasm_write_protect_code_memory)
 #endif  // V8_ENABLE_WEBASSEMBLY