build: allow configure and build in a separate directory

Some .h files in lib/ are autogenerated. The search path should
include the build directory and the source directory. They usually
match but sometimes, they may be different. For example:

 $ mkdir build
 $ cd build
 $ ../configure
 $ make
diff --git a/isisd/Makefile.am b/isisd/Makefile.am
index 26b8ee7..4e9b244 100644
--- a/isisd/Makefile.am
+++ b/isisd/Makefile.am
@@ -1,6 +1,6 @@
 ## Process this file with automake to produce Makefile.in.
 
-INCLUDES = @INCLUDES@ -I.. -I$(top_srcdir) -I$(top_srcdir)/lib \
+INCLUDES = @INCLUDES@ -I.. -I$(top_srcdir) -I$(top_srcdir)/lib -I$(top_builddir)/lib \
 	   @ISIS_TOPOLOGY_INCLUDES@
 DEFS = @DEFS@ -DSYSCONFDIR=\"$(sysconfdir)/\"
 INSTALL_SDATA=@INSTALL@ -m 600
diff --git a/isisd/topology/Makefile.am b/isisd/topology/Makefile.am
index b25497c..ccd2e71 100644
--- a/isisd/topology/Makefile.am
+++ b/isisd/topology/Makefile.am
@@ -1,6 +1,6 @@
 ## Process this file with automake to produce Makefile.in.
 
-INCLUDES = @INCLUDES@ -I.. -I$(top_srcdir) -I$(top_srcdir)/lib
+INCLUDES = @INCLUDES@ -I.. -I$(top_srcdir) -I$(top_srcdir)/lib -I$(top_builddir)/lib
 DEFS = @DEFS@ -DSYSCONFDIR=\"$(sysconfdir)/\"
 
 AM_CFLAGS = $(PICFLAGS)