If a resource file cannot be decoded because the directory is readonly

If a resource file cannot be decoded because the directory is readonly
create a temporary file. This fixes #688011.

Got rid of the install() method in macresource, and replaced it with
a resource_filename() method which will optionally decode a given resourcefile
(which may be applesingle-encoded) and return the real resourcefile.

Use this new method in buildtools to copy the correct resource file to
the bundle. This fixes #688007.