AC_CHECK_HEADER(mach/mach_time.h,,AC_MSG_ERROR($msg_required_header_missing))
AC_CHECK_HEADER(CoreVideo/CVHostTime.h,,AC_MSG_ERROR($msg_required_header_missing))
AC_DEFINE([TARGET_DARWIN], [1], [Darwin target])
AC_CHECK_HEADER(mach/mach_time.h,,AC_MSG_ERROR($msg_required_header_missing))
AC_CHECK_HEADER(CoreVideo/CVHostTime.h,,AC_MSG_ERROR($msg_required_header_missing))
AC_DEFINE([TARGET_DARWIN], [1], [Darwin target])