gpio-tools: init in kernel 5.4

Linux provides some tools to interact with the gpiochip interface (which
replaces the deprecated sysfs GPIO interface). Expose these as a
package.

The tool has not changed much recently, so there is no need to package a
version for each kernel.

pkgs/os-specific/linux/kernel/gpio-utils.nix

@@ -0,0 +1,24 @@
+{ lib, stdenv, linux }:
+
+with lib;
+
+assert versionAtLeast linux.version "4.6";
+
+stdenv.mkDerivation {
+  name = "gpio-utils-${linux.version}";
+
+  inherit (linux) src makeFlags;
+
+  preConfigure = ''
+    cd tools/gpio
+  '';
+
+  separateDebugInfo = true;
+  installFlags = [ "install" "DESTDIR=$(out)" "bindir=/bin" ];
+
+  meta = {
+    description = "Linux tools to inspect the gpiochip interface";
+    maintainers = with stdenv.lib.maintainers; [ kwohlfahrt ];
+    platforms = stdenv.lib.platforms.linux;
+  };
+}

pkgs/top-level/all-packages.nix

@@ -26468,4 +26468,5 @@ in
 
   vpsfree-client = callPackage ../tools/virtualization/vpsfree-client {};
 
+  gpio-utils = callPackage ../os-specific/linux/kernel/gpio-utils.nix { };
 }