NB: this crate won't enable OpenMP unless you also pass -fopenmp to the C compiler (e.g. cc.flag("-fopenmp") in cc-rs). This is solely for linking OpenMP-dependent C libraries with Rust code (in Rust use Rayon, etc.).
libgomp.* present in a directory printed by cc -print-search-dirs,-fopenmp flag set for any C code linked with the Rust program.It should work with recent versions of GCC.
You can set static feature or set OPENMP_STATIC env var to link OpenMP statically, so that executables using it are usable on machines without a compiler installed.
In macOS Clang pretends to be the gcc executable, but doesn't support OpenMP. Install gcc-7 from Homebrew and compile with CC=gcc-7 cargo build. You may need to run cargo clean first if it doesn't take effect.
Static linking is recommended on macOS.