compilation error

Hi Thanks for your great work!

I was trying to install LEMUR on R, however I have encountered this error.
```
ld: warning: directory not found for option '-L/usr/local/gfortran/lib/gcc/x86_64-apple-darwin18/8.2.0'
ld: warning: directory not found for option '-L/usr/local/gfortran/lib'
ld: library not found for -lgfortran
clang: error: linker command failed with exit code 1 (use -v to see invocation)
make: *** [glmGamPoi.so] Error 1
ERROR: compilation failed for package ‘glmGamPoi’
* removing ‘/Library/Frameworks/R.framework/Versions/4.1/Resources/library/glmGamPoi’
Warning: installation of package ‘/var/folders/jp/zptlfyzn5z3dz53d2c0hcft40000gn/T//RtmpDqImAo/file5611ee0480b/glmGamPoi_1.11.8.tar.gz’ had non-zero exit status
```

I have tried to re-install the x-code that you mentioned in another same issue. However, I still give this error. I am using MacBook with M1 chip, will this be a problem?

Thanks in advance!

Kind regards,
Jiayi