Disable v8_embedded_builtins on ppc

ppc is still failing:

https://build.chromium.org/p/client.v8.ports/builders/V8%20Linux%20-%20ppc64%20-%20sim/builds/10180

TBR=yangguo@chromium.org

No-Try: true
No-Presubmit: true
Bug: v8:6666, v8:7571
Change-Id: I99ddc97543b374014587970310ac5172ed514892
Reviewed-on: https://chromium-review.googlesource.com/973005
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#52100}

BUILD.gn

@@ -66,8 +66,10 @@ declare_args() {
   v8_enable_fast_mksnapshot = false
 
   # 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): Support ppc, ia32 and maybe MSVC.
+  v8_enable_embedded_builtins =
+      v8_current_cpu != "x86" && v8_current_cpu != "ppc" &&
+      v8_current_cpu != "ppc64" && (!is_win || is_clang)
 
   # Enable code-generation-time checking of types in the CodeStubAssembler.
   v8_enable_verify_csa = false