Fix detection of IrDA failing with B!=S

Upstream-Status: Pending

Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com>

--- a/acinclude.m4	2014-05-24 14:05:41.757796816 +0100
+++ b/acinclude.m4	2014-05-24 14:03:06.556795536 +0100
@@ -54,6 +54,7 @@
 ])
 
 AC_DEFUN([AC_PATH_IRDA_LINUX], [
+	CPPFLAGS="${CPPFLAGS} -I${srcdir}"
 	AC_CACHE_CHECK([for IrDA support], irda_found, [
 		AC_TRY_COMPILE([
 				#include <sys/socket.h>