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/tests/Makefile.am b/tests/Makefile.am
index 2e98ff7..0c262a4 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -1,4 +1,4 @@
-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@ $(LOCAL_OPTS) -DSYSCONFDIR=\"$(sysconfdir)/\"
AM_CFLAGS = $(PICFLAGS)