Enable memory leak check (#1429)

Report the memory leak info when building iwasm with
`cmake .. -DWAMR_BUILD_GC_VERIFY=1`

core/shared/mem-alloc/mem_alloc.cmake

@@ -6,6 +6,10 @@ set (MEM_ALLOC_DIR ${CMAKE_CURRENT_LIST_DIR})
 
 include_directories(${MEM_ALLOC_DIR})
 
+if (WAMR_BUILD_GC_VERIFY EQUAL 1)
+    add_definitions (-DBH_ENABLE_GC_VERIFY=1)
+endif ()
+
 file (GLOB_RECURSE source_all
       ${MEM_ALLOC_DIR}/ems/*.c
       ${MEM_ALLOC_DIR}/tlsf/*.c