Disable embedded builtins for M67 branch point

Embedding builtins regresses speedometer by roughly 2-3%. Unship
them until M67 is branched.

Bug: v8:6666
Change-Id: Icaddc2cfbc0e52cd6999c648479cb008509a7bf2
Reviewed-on: https://chromium-review.googlesource.com/982053Reviewed-by: Michael Hablich <hablich@chromium.org>
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#52260}

BUILD.gn

@@ -68,7 +68,8 @@ declare_args() {
 
   # Enable embedded builtins.
   # TODO(jgruber,v8:6666): Support ia32 and maybe MSVC.
-  v8_enable_embedded_builtins = v8_current_cpu != "x86" && (!is_win || is_clang)
+  # TODO(jgruber,v8:6666): Re-enable after the M67 branch point.
+  v8_enable_embedded_builtins = false
 
   # Enable code-generation-time checking of types in the CodeStubAssembler.
   v8_enable_verify_csa = false