art的工程已经按照文档配置，但是mdk下编译仍出现报错

modules\api_export\api_export.c(16): error:  #20: identifier "__errno" is undefined
modules\api_export\api_export.c(16): error:  #44: expression must have pointer type
modules\api_export\api_export.c(22): error:  #20: identifier "_impure_ptr" is undefined
modules\api_export\api_export.c(22): error:  #44: expression must have pointer type
modules\plugins\plugins.c(3): error:  #5: cannot open source input file "dlfcn.h": No such file or directory
rt-thread\src\kservice.c(26): error:  #5: cannot open source input file "dlmodule.h": No such file or directory
rt-thread\src\object.c(22): error:  #5: cannot open source input file "dlmodule.h": No such file or directory
rt-thread\components\finsh\msh.c(25): error:  #5: cannot open source input file "dlmodule.h": No such file or directory
rt-thread\src\idle.c(24): error:  #5: cannot open source input file "dlmodule.h": No such file or directory