I would use this vba-m https://sourceforge.net/projects/vbam/
(I don't know if I can post that but if it's removed its the sourceforge link when searching vba-m)
1: Options, link, type, gamecube
2: Options, link, local mode
3: Options, gba, config, boot rom, select bios
4: Options, gba, use bios file
5: close/reopen
6: Launch Dolphin game and open bios file with vba-m
(I don't know if I can post that but if it's removed its the sourceforge link when searching vba-m)
1: Options, link, type, gamecube
2: Options, link, local mode
3: Options, gba, config, boot rom, select bios
4: Options, gba, use bios file
5: close/reopen
6: Launch Dolphin game and open bios file with vba-m