[LLD] Mark a number of x86 only tests to require x86

Noticed while testing for an out of tree target. There are probably more tests that should be so marked.
I'm not sure who owns these tests so I've added a few names I recognise from the recent history.

With advice from probinson, ruiu, rafael and dramatically improved by davidb. Thank you all!

Differential Revision: https://reviews.llvm.org/D34685

llvm-svn: 308335