UnitTest 编译异常汇总：
问题1
Check dependencies
No architectures to compile for (ONLY_ACTIVE_ARCH=YES, active arch=x86_64, VALID_ARCHS=i386).
经过与正常 test target 设置比较，默认设置中 Debug architecture 只有armv7， 添加 arm64以后 Test build 即成功；
问题2
ld: -bundle_loader can only be used with -bundle
clang: error: linker command failed with exit code 1 (use -v to see invocation)
Mach-O 是 mac OS 上的可执行文件格式，在xcode help 文档中，具体是这样描述的，测试target 需选择 Bundle：
问题3
跑test target 碰到如下错误：
ld: entry point (_main) undefined. for architecture armv7
clang: error: linker command failed with exit code 1 (use -v to see invocation)
在test target 中 ， General Tab， 把 Allow testing Host Application APIs 复选框勾上即解决了此问题。
附录：
Mach-O Type (MACH_O_TYPE)
This setting determines the format of the produced binary and how it can be linked when building other binaries. For information on binary types, see Building Mach-O Files in Mach-O Programming Topics.
- Executable: Executables and standalone binaries and cannot be linked. mh_execute
- Dynamic Library: Dynamic libraries are linked at build time and loaded automatically when needed. mh_dylib
- Bundle: Bundle libraries are loaded explicitly at run time. mh_bundle
- Static Library: Static libraries are linked at build time and loaded at execution time. staticlib
- Relocatable Object File: Object files are single-module files that are linked at build time. mh_object