Include the subdirectory so these files will compile from an object build.
%{
#include "h/nmh.h"
#include "h/mh.h"
%{
#include "h/nmh.h"
#include "h/mh.h"
#include "h/utils.h"
#include "h/tws.h"
#include "h/utils.h"
#include "h/tws.h"
#include "h/mh.h"
#include "h/icalendar.h"
#include "icalparse.h"
#include "h/mh.h"
#include "h/icalendar.h"
#include "icalparse.h"
static char *unfold (char *, size_t *);
static void destroy_icallex(void);
static char *unfold (char *, size_t *);
static void destroy_icallex(void);
#include "h/icalendar.h"
#include "h/utils.h"
#include "h/icalendar.h"
#include "h/utils.h"