Remove nonexistent include directory that new compilers complain about.
https://git.congatec.com/yocto/meta-openembedded/-/blob/abc0ec53987b67f07ab64ce4dbd0573cc3d4bd1b/meta-gnome/recipes-gnome/bonobo/files/gcc5.patch
--- tools/browser/Makefile.am.orig
+++ tools/browser/Makefile.am
@@ -2,7 +2,6 @@ INCLUDES =	\
 	-DBONOBO_BROWSER_DATADIR=\""$(datadir)"\"	\
         -DBONOBO_SUPPORT_LOCALEDIR=\""$(datadir)/locale"\"        \
 	-I$(srcdir) -I$(top_srcdir) 			\
-	-I$(top_srcdir)/bonobo-browser			\
 	$(BONOBOUI_CFLAGS)				\
 	$(WARN_CFLAGS)