add piston nix pkg for gcc-fortran

runtimes/default.nix

@@ -48,4 +48,5 @@ args: {
     "gcc-c" = import ./gcc-c.nix args;
     "gcc-c++" = import ./gcc-c++.nix args;
     "gcc-d" = import ./gcc-d.nix args;
+    "gcc-fortran" = import ./gcc-fortran.nix args;
 }

runtimes/gcc-fortran.nix

@@ -0,0 +1,39 @@
+{pkgs, piston, ...}:
+let
+    pkg = pkgs.gfortran;
+in piston.mkRuntime {
+    language = "fortran";
+    version = pkg.version;
+    runtime = "gcc";
+
+    aliases = [
+        "gfortran"
+        "f90"
+    ];
+
+    compile = ''
+        rename 's/.code$/\.f90/' "$@" # Add .f90 extension
+        ${pkg}/bin/gfortran *.f90
+    '';
+
+    run = ''
+        shift
+        ./a.out "$@"
+    '';
+
+    tests = [
+        (piston.mkTest {
+            files = {
+                "test.f90" = ''
+                    program test
+                        print "(a)", 'OK'
+                    end program test
+                '';
+            };
+            args = [];
+            stdin = "";
+            packages = [];
+            main = "test.f90";
+        })
+    ];
+}