config.mk: do not explicitly set CC (#455)

1. `c99` doesn't exist on openbsd
2. `c99` behaves weirdly on macos (doesn't support -Wall)

since make will already set CC (required by POSIX if the implementation
supports C, see `man 1p make`) to something appropriate (or it might be
set in the environment) go ahead and remove explicitly setting it on our
end.

Reviewed-on: https://codeberg.org/nsxiv/nsxiv/pulls/455
Reviewed-by: TAAPArthur <taaparthur@noreply.codeberg.org>

0 files changed, 0 insertions, 0 deletions