the error message could either be related to the reason you described (which is less likely since the used git seems to be newer) or it could be the case that the cert can not be verified.
For the second reason you could try to call git with GIT_SSL_NO_VERIFY / http.sslVerify being disabled.
This is just a guess though.
It is not likely that we will look into the problem more since your package is trying to fetch external resources during the configure phase.
Despite that I might repeat myself: this is highly unrecommended behavior (as mentioned to you several times before).
You might seriously reconsider your workflow - a package following the recommendations will not have the problem in the first place.
- Dirk