add nix-shell file for building with nix

shell.nix

@@ -0,0 +1,49 @@
+# shell.nix
+
+# NOTE we need mkShellNoCC
+# mkShell would add the regular gcc, which has no ada (gnat)
+# https://github.com/NixOS/nixpkgs/issues/142943
+
+with import <nixpkgs> { };
+mkShellNoCC {
+  buildInputs = [
+    ccache
+    cmake
+    curl
+    flashrom
+    git
+    git-lfs
+    gmp
+    gnat12 # gcc with ada
+    hidapi
+    libossp_uuid
+    m4 flex bison # Generate flashmap descriptor parser
+    mpfr
+    ncurses # make menuconfig
+    nss
+    openssl
+    pkg-config
+    python3
+    qemu # test the image
+    rustup
+    util-linux
+    zlib
+  ];
+  shellHook = ''
+    # Set variables for libraries
+    export LD_LIBRARY_PATH=${gmp}/lib:${mpfr}/lib:${zlib}/lib
+
+    # TODO remove?
+    NIX_LDFLAGS="$NIX_LDFLAGS -lncurses"
+
+    # Setup Git repo
+    git lfs install
+    git lfs pull
+    git submodule update --init --recursive --checkout --progress
+
+    # coreboot sdk
+    make -C coreboot CPUS="$(nproc)" crossgcc-i386
+    make -C coreboot CPUS="$(nproc)" crossgcc-x64
+    make -C coreboot gitconfig
+  '';
+}