[builtins] Disable embedded builtins on mips and mips64

Mips big-endian builders don't like embedded builtins. Disable embedded
builtins on mips for now and defer investigation for when there's time.

Example failures:
https://build.chromium.org/p/client.v8.ports/builders/V8%20Mips%20-%20big%20endian%20-%20nosnap%20-%201/builds/6666
https://build.chromium.org/p/client.v8.ports/builders/V8%20Mips%20-%20big%20endian%20-%20nosnap%20-%202/builds/5188

Two issues: test failures due to big-endianness and mismatches in the
isolate-independence list.

TBR=yangguo@chromium.org

Bug: v8:6666
Change-Id: I73750668c03c132a9bb4d4ae9ed2bafd6d91f816
Reviewed-on: https://chromium-review.googlesource.com/955699Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#51848}

BUILD.gn

@@ -65,8 +65,11 @@ 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 mips, mips64, ia32 and maybe MSVC.
+  v8_enable_embedded_builtins =
+      v8_current_cpu != "x86" && v8_current_cpu != "mips" &&
+      v8_current_cpu != "mipsel" && v8_current_cpu != "mips64" &&
+      v8_current_cpu != "mips64el" && (!is_win || is_clang)
 
   # Enable code-generation-time checking of types in the CodeStubAssembler.
   v8_enable_verify_csa = false

test/cctest/test-isolate-independent-builtins.cc

@@ -109,7 +109,6 @@ UNINITIALIZED_TEST(VerifyBuiltinsIsolateIndependence) {
 
   v8_isolate->Dispose();
 }
-#endif  // V8_EMBEDDED_BUILTINS
 
 // V8_CC_MSVC is true for both MSVC and clang on windows. clang can handle
 // __asm__-style inline assembly but MSVC cannot, and thus we need a more
@@ -280,6 +279,7 @@ TEST(ByteInText) {
 }
 #endif  // #ifndef V8_COMPILER_IS_MSVC
 #undef V8_COMPILER_IS_MSVC
+#endif  // V8_EMBEDDED_BUILTINS
 
 #undef FUNCTION_BYTES
 #undef GENERATE_TEST_FUNCTION_DATA