Just in case someone would search for the answer as me.

As @jhasse said it is really easy with Clang. All you need to do is just to build clang with openmp runtime support, so working set of build commands would be like

git clone https://github.com/llvm/llvm-project
cd llvm-project
mkdir build
cd build
cmake -DLLVM_ENABLE_PROJECTS="clang;lld" -DLLVM_ENABLE_RUNTIMES="openmp;compiler-rt" -DLLVM_TARGETS_TO_BUILD="host" -DLLVM_USE_SANITIZER="" -DCMAKE_BUILD_TYPE=Release -DCMAKE_INSTALL_PREFIX=/usr/local/llvm -G "Unix Makefiles" ../llvm

in build directory inside llvm-project one. Then you can also make installation. Or you really can dive into separate OpenMP build.

See also here (there is in-build tool called Archer that was mentioned by @
Simone Atzeni).