clang: error: unsupported option '-fopenmp'

Question

I am on a Mac but I am not a Mac user. I need to run a make command (actually make makewisdom) to compile a software, but my compiler does not recognize some commands:

$ make makewisdom
gcc -I/Users/username/presto/include -I/opt/local/include/glib-2.0 -I/opt/local/lib/glib-2.0/include -I/opt/local/include -I/opt/local/include -I -I/opt/local/include -DUSEFFTW -DUSEMMAP -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64 -g -Wall -W -fPIC -O3 -ffast-math -Wno-unused-result -Wno-unused-but-set-variable -Wno-unused-but-set-parameter -fopenmp -o makewisdom makewisdom.c -L/opt/local/lib -lfftw3f

clang: error: unsupported option '-fopenmp'
clang: error: unsupported option '-fopenmp'
make: *** [makewisdom] Error 1

I know the problem is with clang. I am reading lots of discussions (such this and this, and more), and trying to workaround the problem, but no luck yet. It maybe that I just need to set a different default compiler? (to, for example, gcc, whatever is the version I have installed):

$ gcc --version
Configured with: --prefix=/Library/Developer/CommandLineTools/usr --with-gxx-include-dir=/Library/Developer/CommandLineTools/SDKs/MacOSX10.14.sdk/usr/include/c++/4.2.1
Apple LLVM version 10.0.1 (clang-1001.0.46.4)
Target: x86_64-apple-darwin18.6.0
Thread model: posix
InstalledDir: /Library/Developer/CommandLineTools/usr/bin