diffimg: autotools: add 'lib' to include directories

An upcoming commit need this in order to be able to add an include of
cgraph/exit.h.

Towards https://gitlab.com/graphviz/graphviz/-/issues/2178.

diff --git a/contrib/diffimg/Makefile.am b/contrib/diffimg/Makefile.am
index 772925d4a61609f760d74491467803d601505ee8..c26efa75e55e50f96df70e84252534a83e1acada 100644 (file)
--- a/contrib/diffimg/Makefile.am
+++ b/contrib/diffimg/Makefile.am
@@ -2,7 +2,9 @@
 
 VERSION=0.2
 
-AM_CPPFLAGS = @GDLIB_CFLAGS@
+AM_CPPFLAGS = \
+       @GDLIB_CFLAGS@ \
+       -I$(top_srcdir)/lib
 
 pdfdir = $(pkgdatadir)/doc/pdf