add piston nix pkg for iverilog

runtimes/default.nix

@@ -41,4 +41,5 @@ args: {
     "julia" = import ./julia.nix args;
     "jelly" = import ./jelly.nix args;
     "openjdk-java" = import ./openjdk-java.nix args;
+    "iverilog" = import ./iverilog.nix args;
 }

runtimes/iverilog.nix

@@ -0,0 +1,43 @@
+{pkgs, piston, ...}:
+let
+    pkg = pkgs.verilog;
+in piston.mkRuntime {
+    language = "iverilog";
+    version = pkg.version;
+
+    aliases = [
+        "verilog"
+        "vvp"
+    ];
+
+    compile = ''
+        rename 's/$/\.v/' "$@" # Add .v extension
+        ${pkg}/bin/iverilog *.v
+    '';
+
+    run = ''
+        shift
+        ${pkg}/bin/vvp a.out "$@"
+    '';
+
+    tests = [
+        (piston.mkTest {
+            files = {
+                "test.verilog" = ''
+                    module ok;
+                        initial
+                            begin
+                            $display("OK");
+                            $finish ;
+                            end
+                    endmodule
+
+                '';
+            };
+            args = [];
+            stdin = "";
+            packages = [];
+            main = "test.verilog";
+        })
+    ];
+}