Libclc build issue - `libclc toolchain incomplete - missing tool clang!`

[hamidelmaazouz]

Trying to build a full LLVM release/19.x from source using these settings:

{
    "version": 6,
    "configurePresets": [
        {
            "name": "base",
            "hidden": true,
            "generator": "Ninja",
            "binaryDir": "${sourceDir}/build/${presetName}",
            "installDir": "/opt/llvm/${presetName}",
            "cacheVariables": {
                "CMAKE_C_COMPILER_LAUNCHER": "ccache",
                "CMAKE_C_COMPILER": "/opt/llvm/latest/bin/clang",
                "CMAKE_CXX_COMPILER_LAUNCHER": "ccache",
                "CMAKE_CXX_COMPILER": "/opt/llvm/latest/bin/clang++",
                "BUILD_SHARED_LIBS": "ON",
                "LLVM_CCACHE_BUILD": "ON",
                "LLVM_INCLUDE_TESTS": "ON",
                "LLVM_BUILD_TESTS": "ON",
                "LLVM_BUILD_TOOLS": "ON",
                "LLVM_BUILD_EXAMPLES": "ON",
                "LLVM_ENABLE_ASSERTIONS": "ON",
                "LLVM_ENABLE_RTTI": "ON",
                "LLVM_ENABLE_EH": "OFF",
                "LLVM_USE_LINKER": "lld"
            }
        },
        {
            "name": "llvm-19",
            "displayName": "Configure LLVM-19",
            "inherits": "base",
            "cacheVariables": {
                "CMAKE_BUILD_TYPE": "Release",
                "LLVM_OPTIMIZED_TABLEGEN": "ON",
                "LLVM_ENABLE_PROJECTS": "all",
            	"LLVM_ENABLE_RUNTIMES": "all",
                "LLVM_TARGETS_TO_BUILD": "host"
            }
        }
    ]
}

/opt/llvm/latest/bin/clang is just a custom built Clang from a prior LLVM version (actually 19git when it was still being developed). I then invoked the preset with cmake --preset llvm-19, but the configure phase failed with:

CMake Error at /some/path/llvm-project/libclc/CMakeLists.txt:102 (message):
  libclc toolchain incomplete - missing tool clang!

Any idea what I missed ?