Building LLVM from Source

• Alternatively you might get llvm13 from your package manager, e.g. brew on macos
• git clone https://github.com/llvm/llvm-project.git
• cd llvm-project
• git checkout tags/llvmorg-13.0.0
• mkdir -p build
• cd build
• after each line, there should be a ´\´
• edit the LLVM_BINUTILS_INCDIRcorrectly, or you get a fatal error: 'plugin-api.h' file not found
• for macosx it might be just brew install binutils. I didn't had ld.gold installed, so I did following https://llvm.org/docs/GoldPlugin.html

cmake -G "Unix Makefiles" \
        $xcode \
        -DLLVM_BINUTILS_INCDIR=/usr/local/opt/binutils/include \
        -DLLVM_ABI_BREAKING_CHECKS=FORCE_OFF \
        -DLINK_POLLY_INTO_TOOLS=ON \
        -DLLVM_BUILD_EXTERNAL_COMPILER_RT=ON \
        -DLLVM_BUILD_LLVM_DYLIB=ON \
        -DLLVM_ENABLE_ASSERTIONS=OFF \
        -DLLVM_ENABLE_EH=ON \
        -DLLVM_ENABLE_FFI=ON \
        -DLLVM_ENABLE_LIBCXX=ON \
        -DLLVM_ENABLE_RTTI=ON \
        -DLLVM_INCLUDE_DOCS=OFF \
        -DLLVM_INSTALL_UTILS=ON \
        -DLLVM_OPTIMIZED_TABLEGEN=ON \
        -DLLVM_TARGETS_TO_BUILD=X86 \
        -DLLVM_ENABLE_PROJECTS=clang\;libcxxabi\;libcxx\;lldb\; \
        -DCMAKE_BUILD_TYPE=Release \
        -DWITH_POLLY=ON \
        -DCMAKE_INSTALL_PREFIX=/opt/clasp \
        -DLLVM_CREATE_XCODE_TOOLCHAIN=ON \
        ../llvm

• my cmake tells me, the following, so perhaps these 2 variables need something else or are outdated:

CMake Warning:
  Manually-specified variables were not used by the project:

    LINK_POLLY_INTO_TOOLS
    WITH_POLLY

• cmake --build .

• cmake --build . --target install

• My complete wscript.config on Macos BigSur is the following

LLVM_CONFIG_BINARY = '/opt/clasp/bin/llvm-config'
USE_PARALLEL_BUILD = True
DEBUG_OPTIONS = [  "DEBUG_RELEASE"
                  ,"DEBUG_BCLASP_LISP"
                  ,"DEBUG_CCLASP_LISP"
                  ,"DEBUG_COMPILER"
                  ,"DEBUG_GUARD"
                  ,"DEBUG_VERIFY_MODULES"
# other useful options for debugging
                  ,"USE_HUMAN_READABLE_BITCODE"
                  ,"DEBUG_JIT_LOG_SYMBOLS"
                  ,"DEBUG_ASSERT_TYPE_CAST"
                  ]
REQUIRE_LIBFFI = True
INCLUDES = [ "/Library/Developer/CommandLineTools/usr/include/c++/v1/",
             "/Library/Developer/CommandLineTools/SDKs/MacOSX11.3.sdk/usr/include",
             "/opt/clasp-support/include"]
CPPFLAGS = [ "-Wno-nullability-completeness" ]
LINKFLAGS = ["-L/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/lib" , "-L/opt/clasp-support/lib"]