gfunc.c: fix build error on macOS

[andrew-d]

On macOS Monterey (12.0.1) on a M1 Mac, I'm seeing this build failure:

gfunc.c:296:24: error: format specifies type 'intmax_t' (aka 'long') but the argument has type 'off_t' (aka 'long long') [-Werror,-Wformat]
                        fprintf(out, "%jd", e->f_size);
                                      ~~~   ^~~~~~~~~
                                      %lld
gfunc.c:300:23: error: format specifies type 'intmax_t' (aka 'long') but the argument has type 'off_t' (aka 'long long') [-Werror,-Wformat]
                fprintf(out, "%jd", e->f_size);
                              ~~~   ^~~~~~~~~
                              %lld

I think this is a macOS toolchain bug(?) - off_t should never be larger than intmax_t - but it's easy enough to work around this with some configure-time checks.

[dmitris]

I hit the same issue trying to compile on a Mac.