[yaml2obj][ELF] Don't do disassembly in this test.

This was causing buildbot failures when build without X86 support.

Is there a way to conditionalize the test on the X86 target being
present?

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@184597 91177308-0d34-0410-b5e6-96231b3b80d8