<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/136480>136480</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            llvm-project/libcxx/src/exception.cpp:17:12: fatal error: 'cxxabi.h' file not found
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            libc++
      </td>
    </tr>

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

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

<pre>
    Same issue as #82197. 

<details>

<summary>Full error</summary>

```log
FAILED: libcxx/src/CMakeFiles/cxx_shared.dir/exception.cpp.o
/Users/kip/llvm-project/build/bin/clang++ --target=arm64-apple-darwin23.5.0 -DLIBCXX_BUILDING_LIBCXXABI -DLIBC_NAMESPACE=__llvm_libc_common_utils -D_DEBUG -D_GLIBCXX_ASSERTIONS -D_LIBCPP_BUILDING_LIBRARY -D_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER -D_LIBCPP_REMOVE_TRANSITIVE_INCLUDES -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -I/Users/kip/llvm-project/libcxx/src -I/Users/kip/llvm-project/build/include/c++/v1 -I/Users/kip/llvm-project/cmake/Modules/../../libc -fPIC -fvisibility-inlines-hidden -Werror=date-time -Werror=unguarded-availability-new -Wall -Wextra -Wno-unused-parameter -Wwrite-strings -Wcast-qual -Wmissing-field-initializers -Wimplicit-fallthrough -Wcovered-switch-default -Wno-noexcept-type -Wnon-virtual-dtor -Wdelete-non-virtual-dtor -Wsuggest-override -Wstring-conversion -Wmisleading-indentation -Wctad-maybe-unsupported -fdiagnostics-color -g -std=c++23 -isysroot /Library/Developer/CommandLineTools/SDKs/MacOSX15.2.sdk -mmacosx-version-min=14.5 -fPIC -faligned-allocation -nostdinc++ -fvisibility-inlines-hidden -fvisibility=hidden -fsized-deallocation -Wall -Wextra -Wnewline-eof -Wshadow -Wwrite-strings -Wno-unused-parameter -Wno-long-long -Werror=return-type -Wextra-semi -Wundef -Wunused-template -Wformat-nonliteral -Wzero-length-array -Wdeprecated-redundant-constexpr-static-def -Wno-nullability-completeness -Wno-user-defined-literals -Wno-covered-switch-default -Wno-suggest-override -Wno-error -MD -MT libcxx/src/CMakeFiles/cxx_shared.dir/exception.cpp.o -MF libcxx/src/CMakeFiles/cxx_shared.dir/exception.cpp.o.d -o libcxx/src/CMakeFiles/cxx_shared.dir/exception.cpp.o -c /Users/kip/llvm-project/libcxx/src/exception.cpp
/Users/kip/llvm-project/libcxx/src/exception.cpp:17:12: fatal error: 'cxxabi.h' file not found
   17 | #  include <cxxabi.h>
 |            ^~~~~~~~~~
1 error generated.
```

</details>

Commands:

```sh
$ mkdir build && cd build

$ cmake -DCMAKE_INSTALL_PREFIX=$(pwd)/install-prefix -DCMAKE_C_COMPILER=/opt/homebrew/Cellar/llvm/20.1.2/bin/clang -DCMAKE_CXX_COMPILER=/opt/homebrew/Cellar/llvm/20.1.2/bin/clang++ -DCMAKE_BUILD_TYPE=Debug -DLLVM_ENABLE_PROJECTS="clang;lldb" -DLLVM_TARGETS_TO_BUILD=AArch64 -DLLVM_USE_LINKER=lld -DCMAKE_CXX_STANDARD=20 -DLLVM_BUILD_TESTS=ON -DLLVM_ENABLE_RUNTIMES=libcxx -GNinja ../llvm

$ ninja
```

Configuration:
- Mac M1
- MacOS Sonoma 14.5
- Darwin Kernel Version 23.5.0
- Git commit e8245d53247f155d234e1de647aac2678c49ac28
</pre>
<img width="1" height="1" alt="" src="http://email.email.llvm.org/o/eJy8V01z4jwS_jXKRSWXLRtIDhwcbGfY4SOFySRzcgmrAb0jS15JTsgc9rdvyUDC5J2ana3ZWoqyoT-ebkmPu9vMWrFTAGM0uEWD7Ip1bq_N-LNoP7FGSKeVvdpo_jouWQNYWNsBZhYjGl_T6GYUYBSm_htPODgmpEVx_iayXdMw84rivOikxGCMNiieIFq8a07Gw_D4lXqHwrRIp7M8Q3GKpdjUh4P3MDWixWTOvkEhJFhEi_pwqOyeGeABFwbRAg41tE5oFdRtG2iPS4sHC8ZbfxMtooWUzw1pjf4LaodosemE5P4ulAeUTO0QvUX0FhPimNmBQ3HGTDNMCGtbCYQz8yIUjYNBEGKSzaa3k6en6vZhOsumi7vq-D-9nZ501SKd5-V9OslRnFWVj175JVW1bhqtqs4JaTHJqiy_fbjzP-5OkGlZ5qv1dLkovdQL7-9_iLNKV18vVJ_Sslosq_tVejdPq_Jruc7n1ac8zfLVhdUqny-_5NV6lS7K6Xr6Ja-mi8nsIcv7KFW5zibVZLko1-liXc3TyWp5oSiWq3n6d_FsOp--S6f_acsvT_Q3zM8nJFQtOw7-lI4nhGjxHP0GQN2wb95trnl35E0QnC8-F0y299MJJttnYcVGSOFeiVBSKLBkLzgHhcnjiboZZw6IEw1cyDq165jhwAl7ZkKyE4aCF0wemZTe9OAMw-RRadKpzgInLTOsAQcGk8cXIxwQ64xQO4vJY82sI__smPdshLVC7chWgOREKOEEk-I7GG8omlaKWjiyZVK6vdHdbu_99TMY4MS-CFfvCYct66Q7hlf6-JAQ99pCL1LkWRjXMUm40z4dDhIckJ9obLfbgXXE4xvBvf8xa1Jr9QzGCq2OOUtg3MuF4qAcc0dF7RgnDXvdAOmU7dpWGwccky0XbKe0daK2pNbSB9thYh1HcXY6bhpjIuyrNVo7jGgxExvjKwgtMngGqVvwFWCim4YpPhMK1lpLf9pl9tnf5qxelk_RIKCB5d8waRpWa3sgp7RJIxSKsygJBm-EYNKXRk6YlLo-rcFnyYWqz1XiV6y50KE4e5Na8R044XAJ-5En8OKhCOit3-M94_rlJ0T5OZ2UJlKrXX-5oKkB1xl1Pvc-ErHQCEweO8Vh2997MAdNK5nzZlttGuY8F6RwYHpKfgejiQS1c3vCjGGvPWdaAzVzwIkB3inOlPOksA4OrSHWU6AmxyiehZ18e05q3bSecArseU0WjLcVfvNPcU-qX1H7J-xUmvTLx2SeYTJf_1E7wWRe_BFAwDHRf5hCjf-b-voR4Tc64i_d4zQa-Qv1rXnLHHtr6ilGdFQfDmwjgj2iI7wVErDSDm91pzgKU4xxNMJoNPHDA8aneo5RPHlz66eB3uTigwb5v84fFKbRMSLegQLjCRdcjg9voweixceB5FQbLIrTD0OH3fcbk-DmGxcG9y0HIzpEdIhrfvx_cqEJ7hsKJtlknn72_bNcp7NZdb_Ki-kTijNEE0Sv2xeO6E3ft6xjUpLWwFYc3tx8m53fT2f5qncpdOs3f68b2Bh48bwAKZk5nQ-iBQ2DKKA_jirvaE9P_wu8c1E7ofbTRrX-eu-Hlww2nQ84m32ZV_kivZ3l1f1q-Y98si77kPQIEd9KyTeI0rPtOl3d5euyWi-PgCjO0tTU-2Fytngo82o2XXzuc5eS_7AsP4pk6cq70fDsccosL_vYy8WHvFYPi_V0nnvdkc6Y3C2E-ovhY9f3O_B2nMor_s6hiVZbsetMX6CPlCF4zmo8j84_lyUutdINw75t9NKsHw_xZzAKJP5yaonHcbE3uBMO-9lPOAzXNBnwQUyT0TYaDDiNE4g4DJMRYzUdjq7r5IbV9PqKj2N-E9-wKxhHo2QQJYMkjK_243oY3vBNEg2HySC8pnGUbGk4SDbXozBORjC6EmMa0kGY0DAK42ESB_FgtIkgTsItvY6uRxFKQmiYkIHfkkCb3VU_4Y-jeJhch1eSbUDa_tWAUr-T58mL-lcFM-5Lx6bbWZSEUlhn33GccBLG_5factUZOd471_ZPNi0QLXbC7btNUOvmnfAfcukX6qvgaa3PY_rvAAAA__-CnjaY">