add piston nix pkg for gcc-d

runtimes/default.nix

@@ -47,4 +47,5 @@ args: {
     "go" = import ./go.nix args;
     "gcc-c" = import ./gcc-c.nix args;
     "gcc-c++" = import ./gcc-c++.nix args;
+    "gcc-d" = import ./gcc-d.nix args;
 }

runtimes/gcc-d.nix

@@ -0,0 +1,40 @@
+{pkgs, piston, ...}:
+let
+    pkg = pkgs.gdc;
+in piston.mkRuntime {
+    language = "d";
+    version = pkg.version;
+    runtime = "gcc";
+
+    aliases = [
+        "gdc"
+    ];
+
+    compile = ''
+        rename 's/.code$/\.d/' "$@" # Add .d
+        ${pkg}/bin/gdc *.d
+    '';
+
+    run = ''
+        shift
+        ./a.out "$@"
+    '';
+
+    tests = [
+        (piston.mkTest {
+            files = {
+                "test.d" = ''
+                    import std.stdio;
+
+                    void main() {
+                        writeln("OK");
+                    }
+                '';
+            };
+            args = [];
+            stdin = "";
+            packages = [];
+            main = "test.d";
+        })
+    ];
+}