Compile warning on 32-bit appveyor

../src/lib/tls/x509.c:39:21: error: comparison of integer expressions of different signedness: 'unsigned int' and 'long int' [-Werror=sign-compare]
   39 |   if (cert_lifetime <= min_real_lifetime + start_granularity) {
      |                     ^~
cc1.exe: all warnings being treated as errors