Merge pull request #70515 from peti/t/update-to-gfortran8

gfortran: use version 8 by default to match our C and C++ compiler

pkgs/top-level/all-packages.nix

@@ -7749,7 +7749,8 @@ in
     isl = isl_0_17;
   }));
 
-  gfortran = gfortran7;
+  # Version 8.x is marked broken on Darwin: https://gist.github.com/GrahamcOfBorg/bef0231b7129681950f03c4ac06781c8.
+  gfortran = if stdenv.isDarwin then gfortran7 else gfortran8;
 
   gfortran48 = wrapCC (gcc48.cc.override {
     name = "gfortran";
@@ -14503,7 +14504,6 @@ in
   ### DEVELOPMENT / R MODULES
 
   R = callPackage ../applications/science/math/R {
-    gfortran = gfortran8;
     # TODO: split docs into a separate output
     texLive = texlive.combine {
       inherit (texlive) scheme-small inconsolata helvetic texinfo fancyvrb cm-super;