解决OBJC_CLASS_$_MBProgressHUD无法引用的问题

Undefined symbols for architecture x86_64:
  "_OBJC_CLASS_$_MBProgressHUD", referenced from:
      objc-class-ref in WLBaseViewController.o
ld: symbol(s) not found for architecture x86_64

clang: error: linker command failed with exit code 1 (use -v to see invocation)

在targets ——build settings —— other linker flags 添加 $(inherited）

clean ，build，然后发现build success了。