ld:librarynotfoundfor-lcrt1.3.1.o

clang: warning: libstdc++ is deprecated; move to libc++ with a minimum deployment target of iOS 7 [-Wdeprecated]
ld: library not found for -lcrt1.3.1.o
clang: error: linker command failed with exit code 1 (use -v to see invocation)

解決（Xcode9.4.1）：

1. Build Phases -> Link Binary With Libraries
   新增庫：libc++.tbd。
2. General -> Deployment Info -> Deployment Target
   修改為ios7或者以上版本。