Hello,
the following steps will add the "--enable-auto-import" options for a specific CodeBlocks project:
  1 - Open your project in CodeBlocks.
  2 -Open the menu "Project" -> "Build Options"
  3 -Go in tab "Linker Settings"
  4 -In the text box "Other Link Options", type "--enable-auto-import"
For adding this option as default to ALL project, follow these steps:
  1 - go to menu "Settings" -> "Compiler and Debugger..."
  2 - select your compiler (GNU GCC Compiler) 
  3 -Go in tab "Linker Settings"
  4 -In the text box "Other Link Options", type "--enable-auto-import"