`cabal-install` could print every missing library that is missing from `pkg-config` in one go

[Kleidukos]

I recently provisioned a big app on a new machine and it took several iterations of cabal build before it complained about every missing library in pkg-config. I am not familiar with how the solver knows things, but could it not print one message with all the missing libraries?

cc @grayjay (you are my solver expertjl)

[sebright]

@Kleidukos Do you have an example of the error message that only named one missing pkg-config dependency?