<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/88780>88780</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            -mmacosx-version-min breaks arch detection for compiler-rt
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            new issue
      </td>
    </tr>

    <tr>
      <th>Assignees</th>
      <td>
      </td>
    </tr>

    <tr>
      <th>Reporter</th>
      <td>
          jfgoog
      </td>
    </tr>
</table>

<pre>
    I'm filing this bug as requested by @cjappl in https://github.com/llvm/llvm-project/pull/74394.

As noted in https://github.com/rust-lang/rust/pull/122504#issuecomment-2035091552, passing `-mmacosx-version-min` as a command line seems to break arch detection for compiler-rt.

In compiler-rt/cmake/config-ix.cmake we have:

```cmake
  set(DARWIN_osx_MIN_VER_FLAG "-mmacosx-version-min")

  string(REGEX MATCH "${DARWIN_osx_MIN_VER_FLAG}=([.0-9]+)"
         MACOSX_VERSION_MIN_FLAG "${CMAKE_CXX_FLAGS}")
```

and then, later:

```cmake
 if(NOT MACOSX_VERSION_MIN_FLAG)
    darwin_test_archs(osx
 DARWIN_osx_ARCHS
      ${toolchain_arches})
    message(STATUS "OSX supported arches: ${DARWIN_osx_ARCHS}")
```

So, specifying `-mmacosx-version-min` on Darwin results in no architectures being detected for compiler-rt, and the build therefore fails.

This seems incorrect, and is currently preventing the Rust compiler from updating a key dependency -- the `cc` crate for compiling C and C++ code.

@yln @vitalybuka and @petrhosek: can any of you shed some light here on whether this is expected behavior?
</pre>
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