[libunwind](TestOnly) Mark failing tests as unsupported on Apple targets (#170488)

#167642 introduced a number of test failures on one of our stage 2
builds:
https://ci.swift.org/job/llvm.org/job/clang-stage2-Rthinlto/1403/. This
PR marks these tests as unsupported on `.*-apple.*` targets.
NOKEYCHECK=True
GitOrigin-RevId: 63ea3537d55f75be0d6fb92aef16465b291fa9ed
5 files changed
tree: fbf8ba32833ac6e95827060fecf32af29771493e
  1. cmake/
  2. docs/
  3. include/
  4. src/
  5. test/
  6. .clang-format
  7. CMakeLists.txt
  8. LICENSE.TXT