Would you be interested in the git sources on salsa? [1]
The rules file tends to be the most interesting [2]. This is where the
Debian binary package gets its ./configure and make flags, etc.

B. Stack

[1] https://salsa.debian.org/pkg-voip-team/asterisk
[2] https://salsa.debian.org/pkg-voip-team/asterisk/-/blob/debian/latest/debian/rules