chore: Update V8 flag initialization to use V8 API (#458)

* Set flags via the v8 API, instead of directly modifying them

---------

Signed-off-by: Rachel Green <rachgreen@google.com>

Author: rachgreen33

src/v8/v8.cc

@@ -28,9 +28,10 @@
 
 #include "include/proxy-wasm/limits.h"
 
+#include "absl/strings/str_format.h"
+#include "include/v8-initialization.h"
 #include "include/v8-version.h"
 #include "include/v8.h"
-#include "src/flags/flags.h"
 #include "src/wasm/c-api.h"
 #include "wasm-api/wasm.hh"
 
@@ -42,10 +43,13 @@ wasm::Engine *engine() {
   static wasm::own<wasm::Engine> engine;
 
   std::call_once(init, []() {
-    ::v8::internal::v8_flags.liftoff = false;
-    ::v8::internal::v8_flags.wasm_max_mem_pages =
-        PROXY_WASM_HOST_MAX_WASM_MEMORY_SIZE_BYTES / PROXY_WASM_HOST_WASM_MEMORY_PAGE_SIZE_BYTES;
+    // Disable the Liftoff compiler to force optimized JIT up-front.
+    std::string args = absl::StrFormat("--wasm_max_mem_pages=%u --no-liftoff",
+                                       PROXY_WASM_HOST_MAX_WASM_MEMORY_SIZE_BYTES /
+                                           PROXY_WASM_HOST_WASM_MEMORY_PAGE_SIZE_BYTES);
+    ::v8::V8::SetFlagsFromString(args.c_str(), args.size());
     ::v8::V8::EnableWebAssemblyTrapHandler(true);
+
     engine = wasm::Engine::make();
   });