Split this test into one per supporter nacl arch.

Right now clang produces the same DataLayout for all of them, but it could, for
example, add 'n' specifications when the end architecture is given.

No functionality change, this should just make future changes easier to read.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@197549 91177308-0d34-0410-b5e6-96231b3b80d8