Try to find jansson via pkg-config first, and fall back to checking system defaults if that fails

configure.ac

@@ -132,14 +132,23 @@ AC_CHECK_LIB(pthread, pthread_create, [
         AC_MSG_ERROR([Could not find pthread library - please install libpthread]))
 PTHREAD_LIBS=-lpthread
 
-AC_CHECK_LIB(jansson, json_loads, [
-	JANSSON_LIBS=-ljansson
+PKG_CHECK_MODULES([JANSSON],[jansson],[
+	true
 ],[
-	PKG_CHECK_MODULES([JANSSON],[jansson],[
-		true
+	AC_MSG_CHECKING([for jansson in system-default locations])
+	LIBS="$LIBS -ljansson"
+	AC_TRY_LINK([
+		#include <jansson.h>
+	],[
+		json_object();
+	],[
+		AC_MSG_RESULT([found])
+		JANSSON_LIBS=-ljansson
 	],[
+		AC_MSG_RESULT([not found])
 		AC_MSG_ERROR([Could not find jansson library])
 	])
+	LIBS="${save_LIBS}"
 ])
 AC_SUBST(JANSSON_CFLAGS)
 AC_SUBST(JANSSON_LIBS)

libblkmaker

@@ -1 +1 @@
-Subproject commit 19847fbab02450fb0db2ae519a35808cdc091991
+Subproject commit 482b48bbd5a6dd5a1049801e0e9e5e2512b0aa96