2194be6c92
Commit 232c936ea3 added a fallback ENOTSUP
definition. The check itself and the fallback definition rely on
<errno.h> to be included already, so in case it was not (depending on
the platform) then there will be a wrong definition of ENOTSUP.
Instead of rely on <errno.h> to be included before including a
generated header from this tool, include it manually. This way both
the ENOTSUP check and its fallback definition (if ever) will always
work.