gfortran: fix wrapper host/target offset for cross

Use correct host/target offset for gfortran wrapper, since stdenv
has an implicit offset of -1.

Fixes e.g. pkgsCross.aarch64-multiplatform.buildPackages.gfortran

pkgs/top-level/all-packages.nix

@@ -12694,7 +12694,7 @@ with pkgs;
   gcc_latest = gcc11;
 
   # Use the same GCC version as the one from stdenv by default
-  gfortran = wrapCC (gccStdenv.cc.cc.override {
+  gfortran = wrapCC (gcc.cc.override {
     name = "gfortran";
     langFortran = true;
     langCC = false;