This looks like an accident from a6e427ac
It causes cases like this to fail:

$ cat foo.c
int foo() { return 42; }
$ cat Lib.hs
module Lib where

foreign import ccall "foo" foo :: Int

bar = foo
$ cat cabal-csrc-repl.cabal
cabal-version:      2.4
name:               cabal-csrc-repl
version:            0.1.0.0
library
    exposed-modules:  Lib
    build-depends:    base ^>=4.14.0.0
    C-sources:        foo.c
    default-language: Haskell2010
$ cabal v2-repl
Resolving dependencies...
Build profile: -w ghc-8.10.1 -O1
In order, the following will be built (use -v for more details):
 - cabal-csrc-repl-0.1.0.0 (lib) (first run)
Configuring library for cabal-csrc-repl-0.1.0.0..
Preprocessing library for cabal-csrc-repl-0.1.0.0..
GHCi, version 8.10.1: https://www.haskell.org/ghc/  :? for help
[1 of 1] Compiling Lib              ( Lib.hs, interpreted )
Ok, one module loaded.
*Lib> foo
ghc: ^^ Could not load '_foo', dependency unresolved. See top entry above.