I have cloned the LLVM repository and built Clang and the runtimes using the following sequence of commands, but the file libclang_rt.builtins.a is not produced.
LLVM_ENABLE_RUNTIMES:STRING
Build libc++, libc++abi, libunwind or compiler-rt using the just-built compiler. This is the correct way to build runtimes when putting together a toolchain. It will build the builtins separately from the other runtimes to preserve correct dependency ordering. If you want to build the runtimes using a system compiler, see the libc++ documentation. Note: the list should not have duplicates with LLVM_ENABLE_PROJECTS. The full list is: compiler-rt;libc;libcxx;libcxxabi;libunwind;openmp To enable all of them, use: LLVM_ENABLE_RUNTIMES=all