busybox: fix minimal build with musl libc

Now we always enable large file support, as it should be cheap enough,
and avoids also problems on some filesystems #10181.

The minimal build disables (almost) all options, so it was building
without large file support. However, in musl the `off_t` is *always*
64-bit, which lead to problems, now detected during build time.

pkgs/os-specific/linux/busybox/default.nix

···
     CONFIG_PREFIX "$out"
     CONFIG_INSTALL_NO_USR y
 
+    CONFIG_LFS y
+
     ${stdenv.lib.optionalString enableStatic ''
       CONFIG_STATIC y
     ''}