Custom Preprocess Flag 設置自定義的預處理的方式

OTHER_CFLAGS (Other C Flags)
// 在Target>Build Setting>Custom Compiler Flags>Other C Flags
// 或Target>Build Setting>Swift Compiler>Custom Flags>Other Swift Flags
// 前面要加-D。舉例來說-DRELEASE -DDEVELOPMENT

GCC_PREPROCESSOR_DEFINITIONS (Preprocessor Macros)
// 在Target>Build Setting> Preprocessing > Preprocessor Macros

INFOPLIST_PREPROCESSOR_DEFINITIONS (Info.plist Preprocessor Definitions)
// 在Target>Build Setting> Packaging > Info.plist Preprocessor Definitions