[clang] macCatalyst: add SDKSettings.json as a dependency file if its potentially needed by the compiler (PR #178077)

[Simi Pallipurath via cfe-commits]

simpal01 wrote:

This change appears to break down when running the tests on a cross-compiling build of Clang on a Darwin host.

I am getting the same failures in upstream llvm if i override the default target triple.

```
% cmake -G Ninja -DCMAKE_BUILD_TYPE=Release -DLLVM_ENABLE_PROJECTS="clang;clang-tools-extra"  ../llvm-project-fork/llvm -DLLVM_DEFAULT_TARGET_TRIPLE_DEFAULT="aarch64-unknown-linux-gnu"

% grep LLVM_DEFAULT_TARGET_TRIPLE CMakeCache.txt
LLVM_DEFAULT_TARGET_TRIPLE:STRING=aarch64-unknown-linux-gnu

Failed Tests (12):
  Clang :: ClangScanDeps/P1689.cppm
  Clang :: ClangScanDeps/header_stat_before_open.m
  Clang :: ClangScanDeps/headerwithdirname.cpp
  Clang :: ClangScanDeps/headerwithdirnamefollowedbyinclude.cpp
  Clang :: ClangScanDeps/macro-expansions.cpp
  Clang :: ClangScanDeps/modules.cpp
  Clang :: ClangScanDeps/regular_cdb.cpp
  Clang :: ClangScanDeps/relative_directory.cpp
  Clang :: ClangScanDeps/subframework_header_dir_symlink.m
  Clang :: ClangScanDeps/target-filename.cpp
  Clang :: ClangScanDeps/vfsoverlay.cpp
  Clang :: Frontend/dependency-gen-phony.c

Testing Time: 498.19s

Total Discovered Tests: 50532
  Skipped          :    12 (0.02%)
  Unsupported      :   811 (1.60%)
  Passed           : 49670 (98.29%)
  Expectedly Failed:    27 (0.05%)
  Failed           :    12 (0.02%)
```

If the build does not include any Darwin targets, the tests still run (because the host is Darwin) but fail spuriously due to the absence of a Darwin target in the build.

I’ve opened a follow-up PR to address this by updating the affected tests to add an additional constraint to their REQUIRES annotation: target={{.*}}-(darwin|macos){{.*}}

This ensures the tests only run when the build actually includes a Darwin target, avoiding spurious failures in cross-compiling configurations.

https://github.com/llvm/llvm-project/pull/178077