Fix issue with openmp and clang on ubuntu
Fix issue with openmp and clang on ubuntu

Install missing package libomp-dev
Workaround for clang-tidy script on Travis-CI still required since
libomp-dev is broken

See also:
https://github.com/travis-ci/travis-ci/issues/6073
https://github.com/travis-ci/apt-package-whitelist/issues/3199

BioDynaMo/biodynamo,BioDynaMo/biodynamo,BioDynaMo/biodynamo,BioDynaMo/biodynamo