installdeps: Support NixOS.

Add a `default.nix` with the list of dependencies.

Detect NixOS in installdeps and display the `nix-shell` command to
build.

Signed-off-by: Rafael Kitover <rkitover@gmail.com>

default.nix

@@ -0,0 +1,5 @@
+with import <nixpkgs> {};
+stdenv.mkDerivation {
+    name = "visualboyadvance-m";
+    buildInputs = [ ninja cmake gcc nasm gettext pkg-config ccache zip sfml zlib ffmpeg wxGTK31-gtk3 mesa glfw SDL2 gtk3-x11 ];
+}

installdeps

@@ -177,10 +177,13 @@ linux_installdeps() {
     elif [ -f /etc/gentoo-release ]; then
         gentoo_installdeps
     elif [ -f /etc/os-release ]; then
-        case "$(. /etc/os-release; echo "$ID_LIKE")" in
+        case "$(. /etc/os-release; echo "${ID_LIKE:-$ID}")" in
             *suse*)
                 suse_installdeps
                 ;;
+            nixos)
+                nixos_installdeps
+                ;;
         esac
     elif [ -x /usr/bin/pacman ]; then
         archlinux_installdeps
@@ -807,6 +810,18 @@ suse_installdeps() {
     build_instructions
 }
 
+nixos_installdeps() {
+    nixos=1
+
+    cat <<EOF
+
+To build run:
+
+nix-shell --command 'mkdir build; cd build; $CMAKE .. $cmake_flags -G Ninja; ninja'
+
+EOF
+}
+
 archlinux_require_yaourt() {
     if ! command -v yaourt >/dev/null; then
         (
@@ -1199,3 +1214,5 @@ EOF
 }
 
 main "$@"
+
+# vim:et sw=4: