emacs: properly include source code when withCsrc is true

Previously, we just copied it into a separate directory in the build
directory. That's not useful, and not what was intended.

pkgs/applications/editors/emacs/generic.nix

@@ -142,7 +142,7 @@ in stdenv.mkDerivation {
     rm -rf $siteVersionDir
   '' + lib.optionalString withCsrc ''
     for srcdir in src lisp lwlib ; do
-      dstdir=$siteVersionDir/$srcdir
+      dstdir=$out/share/emacs/$siteVersionDir/$srcdir
       mkdir -p $dstdir
       find $srcdir -name "*.[chm]" -exec cp {} $dstdir \;
       cp $srcdir/TAGS $dstdir