icon-conv-tools: Don't depend on the .nix file at build time

The `src = ./.;` would cause spurious rebuild of the package since the
output hash now depends on the contents of the .nix file.

pkgs/build-support/icon-conv-tools/default.nix

@@ -3,23 +3,23 @@
 stdenv.mkDerivation {
   name = "icon-conv-tools-0.0.0";
 
-  src = ./.;
+  src = ./bin;
 
   buildInputs = [ icoutils ];
 
   patchPhase = ''
-    substituteInPlace "./bin/extractWinRscIconsToStdFreeDesktopDir.sh" \
+    substituteInPlace extractWinRscIconsToStdFreeDesktopDir.sh \
       --replace "icotool" "${icoutils}/bin/icotool" \
       --replace "wrestool" "${icoutils}/bin/wrestool"
   '';
 
   buildPhase = ''
     mkdir -p "$out/bin"
-    cp -p "./bin/"* "$out/bin"
+    cp -p * "$out/bin"
   '';
 
   installPhase = "true";
-  
+
   dontPatchELF = true;
   dontStrip = true;
 
@@ -27,5 +27,4 @@ stdenv.mkDerivation {
     description = "Tools for icon conversion specific to nix package manager";
     maintainers = with stdenv.lib.maintainers; [ jraygauthier ];
   };
-
-}
+}