Move devenv for mcu into subdirectory

mcu/devenv.nix

@@ -0,0 +1,36 @@
+{ pkgs, ... }: {
+  packages = with pkgs; [
+    gnumake
+    cmake
+    pkgsCross.arm-embedded.buildPackages.gdb # ARM one is broken
+    gcc-arm-embedded
+    python3
+    picotool
+    openocd-rp2040
+  ];
+
+  env = {
+    PICO_SDK_PATH = "${pkgs.pico-sdk}/lib/pico-sdk";
+  };
+
+  scripts = {
+    build.exec = ''
+      cmake -S . -B build -D CMAKE_BUILD_TYPE=Debug -D PICO_STDIO_SEMIHOSTING=1
+      cmake --build build --parallel
+    '';
+    build-rel.exec = ''
+      cmake -S . -B build-release -D CMAKE_BUILD_TYPE=Release
+      cmake --build build-release --parallel
+    '';
+    clean.exec = ''
+      rm -rf build/ build-release/
+    '';
+
+    ocd.exec = ''
+      openocd -f ${./tigard-swd.cfg} -f target/rp2040.cfg
+    '';
+    gdb.exec = ''
+      arm-none-eabi-gdb -x .gdbinit build/qclk.elf
+    '';
+  };
+}