with-eigen = [ option.get "with-eigen" ] ;
if ! $(with-eigen) && ! [ test_flags "" : "#include <Eigen/Dense>\nint main() {}" ] {
  with-eigen = "/usr/include/eigen3" ;
}
with-eigen = <include>$(with-eigen) ;
fakelib neural : ..//kenlm wordvecs.cc : $(with-eigen) : : <cxxflags>-fopenmp <linkflags>-fopenmp $(with-eigen) ;
