remove allow-run-as-root in MPIEXEC_PREFLAGS it is handled via the environment variables in the docker images
check for intelclang or clang before checking for OpenMP bug

the wrapper did not compile but since this was not a problem in the last two years it can be removed

Michael Kuron authored 4 years ago and Markus Holzer committed 4 years ago

Some optional components use Boost MultiArray and PropertyTree, so we still include the headers if available.
We also still search std::experimental for any, filesystem and optional because some otherwise C++17-compliant compilers did not support them in std until recently.