Issue linking libextern_draco with openmp enabled

I get a build failure when building WITH_DRACO and WITH_OPENMP

[100%] Linking CXX shared library ../../lib/
ld: error: unable to find library -lomp

I find within <BUILDDIR>/extern/draco/CMakeFiles/extern_draco.dir/ both flags.make and links.txt contain -fopenmp=libomp but there is no -L/dir. I expect this means there is no CMAKE_MODULE_LINKER_FLAGS used with extern/draco but also that the openmp flags are being used needlessly.