Appveyor CI fails on master due to #19506

For some reason, Appveyor CI didn't run on the pull request for #19506 (moved): https://github.com/torproject/tor/pull/216

When #19506 (moved) was merged to master, it failed Appveyor with:

../src/tools/tor-print-ed-signing-cert.c:52:67: error: unknown conversion type character 'z' in format [-Werror=format=]
     fprintf(stderr, "ed25519_cert_parse failed with return value %zd\n",
                                                                   ^
../src/tools/tor-print-ed-signing-cert.c:52:21: error: too many arguments for format [-Werror=format-extra-args]
     fprintf(stderr, "ed25519_cert_parse failed with return value %zd\n",
                     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
../src/tools/tor-print-ed-signing-cert.c:52:67: error: unknown conversion type character 'z' in format [-Werror=format=]
     fprintf(stderr, "ed25519_cert_parse failed with return value %zd\n",
                                                                   ^
../src/tools/tor-print-ed-signing-cert.c:52:21: error: too many arguments for format [-Werror=format-extra-args]
     fprintf(stderr, "ed25519_cert_parse failed with return value %zd\n",
                     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~