make: conditionally link to libsqlite3.
diff --git a/config.h.in b/config.h.in
index 937916c..4c049d2 100644
--- a/config.h.in
+++ b/config.h.in
@@ -18,6 +18,9 @@
 /* Define to 1 if you have the `crypto' library (-lcrypto). */
 #undef HAVE_LIBCRYPTO
 
+/* Define to 1 if you have the `sqlite3' library (-lsqlite3). */
+#undef HAVE_LIBSQLITE3
+
 /* Define to 1 if you have the `memcmp' function. */
 #undef HAVE_MEMCMP