Trying to build compiler-rt:

cmake -G Ninja \
                                                      -DCMAKE_BUILD_TYPE=Release \
                                                      -DCMAKE_C_COMPILER_WORKS=ON \
                                                      -DCMAKE_CXX_COMPILER_WORKS=ON \
                                                      -DCMAKE_CMAKE_MODULE_PATH=../cmake \
                                                      -DCMAKE_MODULE_PATH=/home/jhorak/f/compiler-rt/compiler-rt-17.0.6.src/cmake \
                                                      -DCMAKE_TOOLCHAIN_FILE=(pwd)/wasi-toolchain.cmake \
                                                      -DCOMPILER_RT_BAREMETAL_BUILD=On \
                                                      -DCOMPILER_RT_INCLUDE_TESTS=OFF \
                                                      -DCOMPILER_RT_HAS_FPIC_FLAG=OFF \
                                                      -DCOMPILER_RT_DEFAULT_TARGET_ONLY=On \
                                                      -DCOMPILER_RT_OS_DIR=wasi \
                                                      -DWASI_SDK_PREFIX=/usr \
                                                      -DCMAKE_C_FLAGS="-fno-exceptions --sysroot=/usr/share/wasi-sysroot" \
                                                      -DCMAKE_INSTALL_PREFIX=/usr/lib/clang/17/ \
                                                       \
                                                      lib/builtins


Have the Platform/WASI.cmake with content:
set(WASI 1)

And wasi-toolchain.cmake:
# Cmake toolchain description file for the Makefile

# This is arbitrary, AFAIK, for now.
cmake_minimum_required(VERSION 3.4.0)

set(CMAKE_SYSTEM_NAME WASI)
set(CMAKE_SYSTEM_VERSION 1)
set(CMAKE_SYSTEM_PROCESSOR wasm32)
set(triple wasm32-wasi)

if(WIN32)
  set(WASI_HOST_EXE_SUFFIX ".exe")
else()
  set(WASI_HOST_EXE_SUFFIX "")
endif()

set(CMAKE_C_COMPILER ${WASI_SDK_PREFIX}/bin/clang${WASI_HOST_EXE_SUFFIX})
set(CMAKE_CXX_COMPILER ${WASI_SDK_PREFIX}/bin/clang++${WASI_HOST_EXE_SUFFIX})
set(CMAKE_AR ${WASI_SDK_PREFIX}/bin/llvm-ar${WASI_HOST_EXE_SUFFIX})
set(CMAKE_RANLIB ${WASI_SDK_PREFIX}/bin/llvm-ranlib${WASI_HOST_EXE_SUFFIX})
set(CMAKE_C_COMPILER_TARGET ${triple})
set(CMAKE_CXX_COMPILER_TARGET ${triple})

# Don't look in the sysroot for executables to run during the build
set(CMAKE_FIND_ROOT_PATH_MODE_PROGRAM NEVER)
# Only look in the sysroot (not in the host paths) for the rest
set(CMAKE_FIND_ROOT_PATH_MODE_LIBRARY ONLY)
set(CMAKE_FIND_ROOT_PATH_MODE_INCLUDE ONLY)
set(CMAKE_FIND_ROOT_PATH_MODE_PACKAGE ONLY)


Fails in:
CMake Debug Log at /home/jhorak/f/compiler-rt/compiler-rt-17.0.6.src/cmake/Modules/CompilerRTUtils.cmake:303 (find_package):


  find_package considered the following locations for LLVM's Config module:

    /home/jhorak/f/compiler-rt/compiler-rt-17.0.6.src/CMakeFiles/pkgRedirects/LLVMConfig.cmake
    /home/jhorak/f/compiler-rt/compiler-rt-17.0.6.src/CMakeFiles/pkgRedirects/llvm-config.cmake
    /home/jhorak/f/compiler-rt/compiler-rt-17.0.6.src/lib/builtins/LLVMConfig.cmake
    /home/jhorak/f/compiler-rt/compiler-rt-17.0.6.src/lib/builtins/llvm-config.cmake
    /usr/share/Modules/LLVMConfig.cmake
    /usr/share/Modules/llvm-config.cmake
    /usr/local/LLVMConfig.cmake
    /usr/local/llvm-config.cmake
    /usr/LLVMConfig.cmake
    /usr/llvm-config.cmake
    /usr/lib/llvm16/LLVMConfig.cmake
    /usr/lib/llvm16/llvm-config.cmake
    /usr/share/llvm/LLVMConfig.cmake
    /usr/share/llvm/llvm-config.cmake
    /usr/share/llvm/cmake/LLVMConfig.cmake
    /usr/share/llvm/cmake/llvm-config.cmake
    /var/lib/snapd/snap/LLVMConfig.cmake
    /var/lib/snapd/snap/llvm-config.cmake
    /home/jhorak/LLVMConfig.cmake
    /home/jhorak/llvm-config.cmake
    /home/jhorak/.local/LLVMConfig.cmake
    /home/jhorak/.local/llvm-config.cmake

  The file was not found.


While the non-wasi builds run by:

cmake -GNinja \
                                                  -DCMAKE_BUILD_TYPE=RelWithDebInfo \
                                                  -DCMAKE_MODULE_PATH=/home/jhorak/f/compiler-rt/compiler-rt-17.0.6.src/cmake \
                                                  -DCMAKE_SKIP_RPATH:BOOL=ON \
                                                  -DCOMPILER_RT_INSTALL_PATH=%{_prefix}/lib/clang/%{maj_ver} \
                                                  -DLLVM_ENABLE_PER_TARGET_RUNTIME_DIR=ON \
                                                  \
                                                  -DLLVM_LIBDIR_SUFFIX=64 \
                                                  lib/builtins

finds it:

  find_package considered the following locations for LLVM's Config module:

    /home/jhorak/f/compiler-rt/compiler-rt-17.0.6.src/CMakeFiles/pkgRedirects/LLVMConfig.cmake
    /home/jhorak/f/compiler-rt/compiler-rt-17.0.6.src/CMakeFiles/pkgRedirects/llvm-config.cmake
    /home/jhorak/f/compiler-rt/compiler-rt-17.0.6.src/lib/builtins/LLVMConfig.cmake
    /home/jhorak/f/compiler-rt/compiler-rt-17.0.6.src/lib/builtins/llvm-config.cmake
    /usr/share/Modules/LLVMConfig.cmake
    /usr/share/Modules/llvm-config.cmake
    /usr/local/LLVMConfig.cmake
    /usr/local/llvm-config.cmake
    /usr/LLVMConfig.cmake
    /usr/llvm-config.cmake
    /usr/lib64/cmake/llvm/LLVMConfig.cmake

  The file was found at

    /usr/lib64/cmake/llvm/LLVMConfig.cmake