Fix x86 build

When building for x86, WebKit uses JSC, not V8. However, we still need
to make sure that the V8 makefile does not try to build V8.

See https://android-git.corp.google.com/g/#change,112847

Change-Id: Id7df890c7bae581d6f955a4d51f9b68bb478dcba
1 file changed