gcc compile, getting "clang: error: unsupported option '-fopenmp'"

I am running the command

gcc -o openmptest -fopenmp openmptest.c

however am getting the error:

clang: error: unsupported option '-fopenmp'

I am running this on Mac Mojave. In addition I am using VS code which is telling me

cannot open source file "omp.h"

for my include statement.