templates: add 'system-flake' template

templates/system-flake/pkgs/config/default.nix

@@ -0,0 +1,5 @@
+lib:
+with lib; {
+  android_sdk.accept_license = true;
+  allowUnfreePredicate = pkg: import ./unfree.nix lib (getName pkg);
+}

templates/system-flake/pkgs/config/unfree.nix

@@ -0,0 +1,7 @@
+lib: name:
+with lib;
+  elem name [
+    "libproprietary-v3"
+    "closed-source-pkg"
+    "favorite-abandonware"
+  ]

templates/system-flake/pkgs/default.nix

@@ -0,0 +1,12 @@
+final: prev:
+with prev.lib; let
+  inherit (final) callPackage fetchpatch;
+in {
+  lib = callPackage ./lib {};
+
+  hello-world = callPackage ./hello-world {};
+
+  override = {
+    sl = prev.sl.overrideAttrs {pname = "my-sl";};
+  };
+}

templates/system-flake/pkgs/hello-world/Makefile

@@ -0,0 +1,6 @@
+CFLAGS += -O3 -s
+
+all: hello-world
+
+%: %.c
+	$(CC) $(CFLAGS) -o $@ $<

templates/system-flake/pkgs/hello-world/default.nix

@@ -0,0 +1,14 @@
+{stdenv, ...}:
+stdenv.mkDerivation {
+  name = "hello-world";
+  version = "1.0.0";
+
+  src = ./.;
+
+  installPhase = ''
+    mkdir -p $out/bin
+    cp hello-world $out/bin
+  '';
+
+  meta.mainProgram = "hello-world";
+}

templates/system-flake/pkgs/hello-world/hello-world.c

@@ -0,0 +1,7 @@
+#include <stdio.h>
+
+int main()
+{
+	printf("Hello, world!\n");
+	return 0;
+}

templates/system-flake/pkgs/lib/default.nix

@@ -0,0 +1,3 @@
+{callPackage}: {
+  fibonacci = callPackage ./fibonacci.nix {};
+}

templates/system-flake/pkgs/lib/fibonacci.nix

@@ -0,0 +1,7 @@
+let
+  fib = n:
+    if n > 1
+    then fib (n - 1) + fib (n - 2)
+    else 1;
+in
+  fib