[Vala] How to make the CCode contains the local header ?

["G.S.Alex" <sthots gmail com>]

When i write a vapi file to use some c code files , i use the
cheader_filename attribute to include the header file.
But the default generated code will use the system headers. For example :

        [CCode(cheader_filename = "case.h"]
will be
        #include <case.h>
not
        #include "case.h"

so , what should I do if i want to use the file in the current directory ?