pimd: fix out of tree build

pimd/Makefile.am was missing srcdir/lib from its include paths, breaking
out-of-tree build regarding route_types.h

Signed-off-by: David Lamparter <equinox@opensourcerouting.org>
diff --git a/pimd/Makefile.am b/pimd/Makefile.am
index 816afb9..b82613a 100644
--- a/pimd/Makefile.am
+++ b/pimd/Makefile.am
@@ -34,7 +34,7 @@
 PIM_DEFS += -DPIM_ENFORCE_LOOPFREE_MFC
 #PIM_DEFS += -DPIM_UNEXPECTED_KERNEL_UPCALL
 
-AM_CPPFLAGS = -I.. -I$(top_srcdir) -I$(top_srcdir)/lib
+AM_CPPFLAGS = -I.. -I$(top_srcdir) -I$(top_srcdir)/lib -I$(top_builddir)/lib
 DEFS = @DEFS@ -DSYSCONFDIR=\"$(sysconfdir)/\" $(PIM_DEFS)
 INSTALL_SDATA=@INSTALL@ -m 600
 LIBS = @LIBS@