printf("%zd") of ssize_t variables results in a warning

[heatd]

It is possible that the ssize_t definition is just slightly wrong for some targets.

From IRC: https://gist.github.com/heatd/844f6bb11370b66468669098bb918a4d

Example warnings: https://gist.github.com/heatd/3a0ba9c7710706d6298572018ef573a1