MacOS R-devel builds failing because gfortran is not found #724
Description
Describe the bug
The deldir package has some Fortran in it. I have R CMD check actions failing on MacOS R-devel (since the release of R 4.3.0) because deldir is failing to install. It gets a bunch of warnings; I think those don't matter. Then it fails when some gfortran libs are not found.
To Reproduce
I've set up a small testpkg that doesn't do anything, but it imports deldir. The check log here:
https://github.com/dmurdoch/testpkg/actions/runs/4861226608/jobs/8666011526
ends with this error:
clang -mmacosx-version-min=10.13 -dynamiclib -Wl,-headerpad_max_install_names -undefined dynamic_lookup -single_module -multiply_defined suppress -L/Library/Frameworks/R.framework/Resources/lib -L/usr/local/lib -o deldir.so acchk.o addpt.o adjchk.o binsrt.o circen.o cross.o crossutil.o delet.o delet1.o delout.o delseg.o dirout.o dirseg.o dldins.o init.o initad.o insrt.o insrt1.o intri.o locn.o master.o mnnd.o pred.o qtest.o qtest1.o stoke.o succ.o swap.o testeq.o triar.o trifnd.o -L/usr/local/gfortran/lib/gcc/x86_64-apple-darwin18/8.2.0 -L/usr/local/gfortran/lib -lgfortran -lquadmath -lm -F/Library/Frameworks/R.framework/.. -framework R -Wl,-framework -Wl,CoreFoundation
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: *** [deldir.so] Error 1
ERROR: compilation failed for package ‘deldir’
* removing ‘/private/var/folders/24/8k48jl6d249_n_qfxwsl6xvm0000gn/T/RtmpotXreJ/pkg-libd9a608a2256/deldir’
Expected behavior
deldir is buildable on other platforms. I don't think it is doing anything fancy about libs; those are just the R defaults, so it should install.