split gateware building into individual derivations

pkgs/cynthion/single-gateware.nix

@@ -0,0 +1,41 @@
+{
+  stdenvNoCC,
+  cynthion-unwrapped,
+  zsh,
+  yosys,
+  nextpnr,
+  trellis,
+  bitstream ? null,
+  platform ? null,
+  ...
+}: stdenvNoCC.mkDerivation {
+  pname = "cynthion-gateware-${bitstream}";
+  version = "${cynthion-unwrapped.version}-${platform}";
+
+  inherit (cynthion-unwrapped) src;
+  dontFixup = true;
+
+  nativeBuildInputs = [
+    cynthion-unwrapped
+    yosys
+    nextpnr
+    trellis
+    zsh
+  ];
+
+  LUNA_PLATFORM = "cynthion.gateware.platform:${platform}";
+
+  buildPhase = ''
+    runHook preBuild
+
+    mkdir -p assets/${platform}
+    python -m cynthion.gateware.${bitstream}.top --dry-run --output assets/${platform}/${bitstream}.bit
+
+    runHook postBuild
+  '';
+
+  installPhase = ''
+    mkdir -p $out/share
+    cp -r assets $out/share
+  '';
+}