Fix clang compilation warnings and a link failure.

src/lib/small/slab_cache.c

@@ -70,8 +70,10 @@ slab_assert(struct slab_cache *cache, struct slab *slab)
 	assert(slab->order <= cache->order_max + 1);
 	if (slab->order <= cache->order_max) {
 		size_t size = slab_order_size(cache, slab->order);
+		(void) size;
 		assert(slab->size == size);
 		intptr_t addr = (intptr_t) slab;
+		(void) addr;
 		assert(addr == (addr & ~(size - 1)));
 	}
 }

test/unit/CMakeLists.txt

@@ -29,7 +29,7 @@ add_executable(lf_lifo.test lf_lifo.c)
 add_executable(slab_arena.test slab_arena.c)
 target_link_libraries(slab_arena.test small)
 add_executable(arena_mt.test arena_mt.c)
-target_link_libraries(arena_mt.test small)
+target_link_libraries(arena_mt.test small pthread)
 
 set(MSGPUCK_DIR ${PROJECT_SOURCE_DIR}/src/lib/msgpuck/)
 add_executable(msgpack.test