toybox: install all binary links in one directory

also...
- removes an unused parameter
- patches all shebangs, not just those in "scripts" dir
- add "which" to checkInputs for debug mode tests

pkgs/tools/misc/toybox/default.nix

@@ -1,5 +1,5 @@
 {
-  stdenv, lib, fetchFromGitHub, buildPackages,
+  stdenv, lib, fetchFromGitHub, which,
   enableStatic ? false,
   enableMinimal ? false,
   extraConfig ? ""
@@ -19,7 +19,7 @@ stdenv.mkDerivation rec {
 
   buildInputs = lib.optionals enableStatic [ stdenv.cc.libc stdenv.cc.libc.static ];
 
-  postPatch = "patchShebangs scripts";
+  postPatch = "patchShebangs .";
 
   inherit extraConfig;
   passAsFile = [ "extraConfig" ];
@@ -43,12 +43,15 @@ stdenv.mkDerivation rec {
     make oldconfig
   '';
 
-  makeFlags = [ "PREFIX=$(out)" ] ++ lib.optional enableStatic "LDFLAGS=--static";
+  makeFlags = [ "PREFIX=$(out)/bin" ] ++ lib.optional enableStatic "LDFLAGS=--static";
+
+  installTargets = "install_flat";
 
   # tests currently (as of 0.8.0) get stuck in an infinite loop...
   # ...this is fixed in latest git, so doCheck can likely be enabled for next release
   # see https://github.com/landley/toybox/commit/b928ec480cd73fd83511c0f5ca786d1b9f3167c3
   #doCheck = true;
+  checkInputs = [ which ]; # used for tests with checkFlags = [ "DEBUG=true" ];
   checkTarget = "tests";
 
   meta = with stdenv.lib; {