How about make target completion as in https://github.com/mg979/tasks.vim/blob/559175d47ea8fd7f48916882874484e22c55c557/autoload/async/make.vim for the make compiler in https://github.com/tpope/vim-dispatch/blob/a2ff28abdb2d89725192db5b8562977d392a4d3f/autoload/dispatch.vim#L732 ?
How about make target completion as in https://github.com/mg979/tasks.vim/blob/559175d47ea8fd7f48916882874484e22c55c557/autoload/async/make.vim for the make compiler in
vim-dispatch/autoload/dispatch.vim
Line 732 in a2ff28a