Installation Error - 'gsl/gsl_poly.h' file not found

[astrojenni]

I am trying to install this with pip and I am having issues with it finding gsl. I have tried both installing gsl with homebrew & adding the relevant folders to my path, and installing with MacPorts. In my virtual environment for planetplanet, if I do the command 'which gsl-config' I successfully get the location as '/opt/local/bin/gsl-config', which is where the MacPorts installation appeared.

However, when I try to pip install planetplanet, I get the following error:

clang -fno-strict-overflow -Wsign-compare -Wunreachable-code -fno-common -dynamic -DNDEBUG -g -O3 -Wall -arch arm64 -arch x86_64 -g -DLIBREBOUND -Irebound/src/ -Iprogress/ -Iplanetplanet/photo/ -I/usr/local/include -I/Users/j.french.4@bham.ac.uk/venvs/planetplanet/include -I/Library/Frameworks/Python.framework/Versions/3.12/include/python3.12 -c planetplanet/photo/eyeball.c -o build/temp.macosx-10.13-universal2-cpython-312/planetplanet/photo/eyeball.o -Wall -I/usr/local/include -fstrict-aliasing -O3 -std=c99 -Wno-unknown-pragmas -DLIBREBOUND -D_GNU_SOURCE -fPIC
      planetplanet/photo/eyeball.c:10:10: fatal error: 'gsl/gsl_poly.h' file not found
         10 | #include <gsl/gsl_poly.h>
            |          ^~~~~~~~~~~~~~~~
      1 error generated.
      error: command '/usr/bin/clang' failed with exit code 1
      [end of output]
  
  note: This error originates from a subprocess, and is likely not a problem with pip.
  ERROR: Failed building wheel for planetplanet
Failed to build planetplanet