busybox

Revert "libbb: remove unnecessary variable in xmalloc_fgets"

The variable is in fact necessary.

    commit 2da9724b56169f00bd7fb6b9a11c9409a7620981
    Author: Quentin Rameau <quinq@fifth.space>
    Date:   Sun Apr 1 17:05:35 2018 +0200
        libbb: remove unnecessary variable in xmalloc_fgets

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>