[test] XFAIL two tests with inlining debug info issues on Sparc

Currently only two test failures remain on Sparc, both
`sparcv9-sun-solaris2.11` and `sparc64-unknown-linux-gnu`:

  LLVM :: DebugInfo/Generic/debug-label-inline.ll
  LLVM :: Linker/subprogram-linkonce-weak.ll

They seem related in that debug info isn't generated for instruction
bundles (like `retl+add` in the delay slot).

I've filed separate bugs for both files (Bug 47129 and 47131), though it's
probably the same issue.

This patch `XFAIL`s the tests.

Tested on `sparcv9-sun-solaris2.11` and `amd64-pc-solaris2.11`.

Differential Revision: https://reviews.llvm.org/D85827