nss: Just delete files if includeTools is false.

Before, the entire directory was deleted and recreated, which fails if we want
to sign libraries (shlibsign is obviously deleted in that step as well), so we
delete everything but "nss-config" on postFixup.

pkgs/development/libraries/nss/default.nix

@@ -65,7 +65,6 @@ in stdenv.mkDerivation rec {
     mv $out/public $out/include
     mv $out/*.OBJ/* $out/
     rmdir $out/*.OBJ
-    ${if includeTools then "" else "rm -rf $out/bin; mkdir $out/bin"}
 
     cp -av config/nss-config $out/bin/nss-config
   '';
@@ -76,5 +75,7 @@ in stdenv.mkDerivation rec {
       libfile="$out/lib/lib$libname.so"
       LD_LIBRARY_PATH=$out/lib $out/bin/shlibsign -v -i "$libfile"
     done
+  '' + stdenv.lib.optionalString (!includeTools) ''
+    find $out/bin -type f \( -name nss-config -o -delete \)
   '';
 }