example/main: add missing $(DESTDIR) to standard include path

This is used everywhere else so looks loke a simple omission.  Needed
when cross-compiling (or packaging) Clixon.

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>

example/main/Makefile.in

@@ -69,7 +69,7 @@ endif
 
 with_restconf	= @with_restconf@
 
-INCLUDES 	= -I$(includedir) @INCLUDES@ 
+INCLUDES 	= -I$(DESTDIR)$(includedir) @INCLUDES@
 LINKAGE         = @LINKAGE@
 LDFLAGS 	= @LDFLAGS@
 CPPFLAGS  	= @CPPFLAGS@