ExternalProject_Add(compiler-rt
    DEPENDS llvm-config clang ${compiler_rt_configure_deps}
    PREFIX ${COMPILER_RT_PREFIX}
    SOURCE_DIR ${COMPILER_RT_SRC_ROOT}
    STAMP_DIR ${STAMP_DIR}
    BINARY_DIR ${BINARY_DIR}
    CMAKE_ARGS ${CLANG_COMPILER_RT_CMAKE_ARGS}
               -DCMAKE_C_COMPILER=${LLVM_RUNTIME_OUTPUT_INTDIR}/clang
               -DCMAKE_CXX_COMPILER=${LLVM_RUNTIME_OUTPUT_INTDIR}/clang++
               -DCMAKE_ASM_COMPILER=${LLVM_RUNTIME_OUTPUT_INTDIR}/clang
               -DCMAKE_BUILD_TYPE=${CMAKE_BUILD_TYPE}
               -DCMAKE_MAKE_PROGRAM=${CMAKE_MAKE_PROGRAM}
               -DCMAKE_C_COMPILER_LAUNCHER=${CMAKE_C_COMPILER_LAUNCHER}
               -DCMAKE_CXX_COMPILER_LAUNCHER=${CMAKE_CXX_COMPILER_LAUNCHER}
               -DLLVM_CONFIG_PATH=${LLVM_RUNTIME_OUTPUT_INTDIR}/llvm-config
               -DLLVM_LIT_ARGS=${LLVM_LIT_ARGS}
               -DCOMPILER_RT_OUTPUT_DIR=${output_resource_dir}
               -DCOMPILER_RT_EXEC_OUTPUT_DIR=${LLVM_RUNTIME_OUTPUT_INTDIR}
               -DCOMPILER_RT_INSTALL_PATH:PATH=${install_resource_dir}
               -DCOMPILER_RT_INCLUDE_TESTS=${LLVM_INCLUDE_TESTS}
               -DCMAKE_INSTALL_PREFIX=${CMAKE_INSTALL_PREFIX}
               -DLLVM_LIBDIR_SUFFIX=${LLVM_LIBDIR_SUFFIX}
               -DLLVM_RUNTIME_OUTPUT_INTDIR=${LLVM_RUNTIME_OUTPUT_INTDIR}
               -DCMAKE_OSX_DEPLOYMENT_TARGET=${CMAKE_OSX_DEPLOYMENT_TARGET}
               -DCMAKE_OSX_SYSROOT:PATH=${CMAKE_OSX_SYSROOT}
               ${COMPILER_RT_PASSTHROUGH_VARIABLES}
    INSTALL_COMMAND ""
    STEP_TARGETS configure build
    USES_TERMINAL_CONFIGURE 1
    USES_TERMINAL_BUILD 1
    USES_TERMINAL_INSTALL 1
    # Always run the build command so that incremental builds are correct.
    BUILD_ALWAYS 1
    )

ExternalProject_Add(
    ${ABSL_PROJECT}
    PREFIX absl
    URL ${ABSL_TAR_URL}
    URL_MD5 52b9786ca6fbc679869fee2b6fef25a5
    UPDATE_COMMAND ""
    BUILD_BYPRODUCTS ${ABSL_STATIC_LIBRARIES}
    CMAKE_CACHE_ARGS
      -DCMAKE_C_COMPILER_LAUNCHER:STRING=${CMAKE_C_COMPILER_LAUNCHER}
      -DCMAKE_CXX_COMPILER_LAUNCHER:STRING=${CMAKE_CXX_COMPILER_LAUNCHER}
      -DCMAKE_INSTALL_PREFIX:PATH=${ABSL_INSTALL}
      -DCMAKE_INSTALL_LIBDIR:PATH=${ABSL_INSTALL}/${CMAKE_INSTALL_LIBDIR}
      -DCMAKE_INSTALL_MESSAGE:STRING=${CMAKE_INSTALL_MESSAGE}
      -DCMAKE_POSITION_INDEPENDENT_CODE:BOOL=ON
      -DCMAKE_BUILD_TYPE:STRING=${CMAKE_BUILD_TYPE})

ExternalProject_Add(${GTEST_TARGET}
    PREFIX ${GTEST_TARGET}
    GIT_REPOSITORY https://github.com/google/googletest.git
    GIT_TAG v1.14.0
    UPDATE_COMMAND ""
    CMAKE_CACHE_ARGS -DCMAKE_C_COMPILER:FILEPATH=${CMAKE_C_COMPILER}
                     -DCMAKE_CXX_COMPILER:FILEPATH=${CMAKE_CXX_COMPILER}
                     -DCMAKE_C_COMPILER_LAUNCHER:FILEPATH=${CMAKE_C_COMPILER_LAUNCHER}
                     -DCMAKE_CXX_COMPILER_LAUNCHER:FILEPATH=${CMAKE_CXX_COMPILER_LAUNCHER}
    CMAKE_ARGS ${CMAKE_ARGS}
               -DCMAKE_INSTALL_PREFIX=${GTEST_INSTALL_DIR}
               -DCMAKE_INSTALL_LIBDIR=lib
    BUILD_BYPRODUCTS ${GTEST_BUILD_BYPRODUCTS}
)

set(CMAKE_C_COMPILER_LAUNCHER "${ccache_path}")

ExternalProject_Add(
      fftwf
      PREFIX fftwf-${_fftw_target_version}
      INSTALL_DIR ${FFTW_STAGED_INSTALL_PREFIX}
      URL
        ${_fftw_url}
      URL_HASH SHA512=${_fftw_url_hash}
      DOWNLOAD_NAME "fftw-${_fftw_target_version}.tar.gz"
      DOWNLOAD_NO_PROGRESS 1
      UPDATE_COMMAND
        ""
      LOG_CONFIGURE 1
      LOG_BUILD 1
      LOG_INSTALL 1
      CMAKE_CACHE_ARGS
        -DBUILD_SHARED_LIBS:BOOL=${BUILD_SHARED_LIBS} -DBUILD_TESTS:BOOL=OFF
        -DCMAKE_BUILD_TYPE:STRING=${FFTW_BUILD_TYPE}
        -DCMAKE_INSTALL_PREFIX:PATH=${FFTW_STAGED_INSTALL_PREFIX}
        -DCMAKE_INSTALL_LIBDIR:STRING=${CMAKE_INSTALL_LIBDIR}
        -DCMAKE_INSTALL_BINDIR:STRING=${CMAKE_INSTALL_BINDIR}
        -DDISABLE_FORTRAN:BOOL=ON -DENABLE_AVX:BOOL=OFF -DENABLE_AVX2:BOOL=OFF
        -DENABLE_FLOAT:BOOL=ON -DENABLE_LONG_DOUBLE:BOOL=OFF
        -DENABLE_OPENMP:BOOL=OFF -DENABLE_QUAD_PRECISION:BOOL=OFF
        -DENABLE_SSE:BOOL=OFF -DENABLE_SSE2:BOOL=OFF -DENABLE_THREADS:BOOL=ON
        -DCMAKE_APPLE_SILICON_PROCESSOR:STRING=${CMAKE_APPLE_SILICON_PROCESSOR}
        -DCMAKE_C_COMPILER_LAUNCHER:PATH=${CMAKE_C_COMPILER_LAUNCHER}
        -DCMAKE_C_COMPILER:PATH=${CMAKE_C_COMPILER}
        -DCMAKE_C_FLAGS:STRING=${CMAKE_C_FLAGS}
        -DCMAKE_OSX_SYSROOT:PATH=${CMAKE_OSX_SYSROOT}
        -DCMAKE_OSX_DEPLOYMENT_TARGET:PATH=${CMAKE_OSX_DEPLOYMENT_TARGET}
        -DCMAKE_OSX_ARCHITECTURES:STRING=${CMAKE_OSX_ARCHITECTURES}
        -DCMAKE_POSITION_INDEPENDENT_CODE:BOOL=${CMAKE_POSITION_INDEPENDENT_CODE}
        -DCMAKE_POLICY_VERSION_MINIMUM:STRING=${ITK_OLDEST_VALIDATED_POLICIES_VERSION}
    )

add_custom_command(OUTPUT "${LL}"
                                   COMMAND ${CMAKE_CROSSCOMPILING_EMULATOR} ${CMAKE_C_COMPILER_LAUNCHER} $<TARGET_FILE:clang> ${clang_flags} -o "${LL}" "$<SHELL_PATH:${SOURCE}>"
                                   DEPENDS $<TARGET_NAME:clang> "${SOURCE}"
                                   DEPFILE "${basename}.d"
                                   VERBATIM)

message(STATUS "Using custom C compiler launcher: ${CMAKE_C_COMPILER_LAUNCHER}")

ExternalProject_Add(compiler-rt
    DEPENDS llvm-config clang ${compiler_rt_configure_deps}
    PREFIX ${COMPILER_RT_PREFIX}
    SOURCE_DIR ${COMPILER_RT_SRC_ROOT}
    STAMP_DIR ${STAMP_DIR}
    BINARY_DIR ${BINARY_DIR}
    CMAKE_ARGS ${CLANG_COMPILER_RT_CMAKE_ARGS}
               -DCMAKE_C_COMPILER=${LLVM_RUNTIME_OUTPUT_INTDIR}/clang
               -DCMAKE_CXX_COMPILER=${LLVM_RUNTIME_OUTPUT_INTDIR}/clang++
               -DCMAKE_ASM_COMPILER=${LLVM_RUNTIME_OUTPUT_INTDIR}/clang
               -DCMAKE_BUILD_TYPE=${CMAKE_BUILD_TYPE}
               -DCMAKE_MAKE_PROGRAM=${CMAKE_MAKE_PROGRAM}
               -DCMAKE_C_COMPILER_LAUNCHER=${CMAKE_C_COMPILER_LAUNCHER}
               -DCMAKE_CXX_COMPILER_LAUNCHER=${CMAKE_CXX_COMPILER_LAUNCHER}
               -DLLVM_CONFIG_PATH=${LLVM_RUNTIME_OUTPUT_INTDIR}/llvm-config
               -DLLVM_LIT_ARGS=${LLVM_LIT_ARGS}
               -DCOMPILER_RT_OUTPUT_DIR=${output_resource_dir}
               -DCOMPILER_RT_EXEC_OUTPUT_DIR=${LLVM_RUNTIME_OUTPUT_INTDIR}
               -DCOMPILER_RT_INSTALL_PATH:PATH=${install_resource_dir}
               -DCOMPILER_RT_INCLUDE_TESTS=${LLVM_INCLUDE_TESTS}
               -DCMAKE_INSTALL_PREFIX=${CMAKE_INSTALL_PREFIX}
               -DLLVM_LIBDIR_SUFFIX=${LLVM_LIBDIR_SUFFIX}
               -DLLVM_RUNTIME_OUTPUT_INTDIR=${LLVM_RUNTIME_OUTPUT_INTDIR}
               -DCMAKE_OSX_DEPLOYMENT_TARGET=${CMAKE_OSX_DEPLOYMENT_TARGET}
               -DCMAKE_OSX_SYSROOT:PATH=${CMAKE_OSX_SYSROOT}
               ${COMPILER_RT_PASSTHROUGH_VARIABLES}
    INSTALL_COMMAND ""
    STEP_TARGETS configure build
    USES_TERMINAL_CONFIGURE 1
    USES_TERMINAL_BUILD 1
    USES_TERMINAL_INSTALL 1
    # Always run the build command so that incremental builds are correct.
    BUILD_ALWAYS 1
    )