The easiest thing to do may be to look at the build logs for the package in question. You can find them by starting at, e.g., https://launchpad.net/ubuntu/+source/asterisk, then follow the link for the version you care about (in this case, https://launchpad.net/ubuntu/maverick/+source/asterisk/1:126.96.36.199-1ubuntu1.1)
Under the "Builds" header, you'll see a link for each architecture the package was built on. Don't worry about this too much, and just pick one - I'll look at amd64.
On the build record page, there's a link to the buildlog - https://launchpadlibrarian.net/62593317/buildlog_ubuntu-maverick-amd64.asterisk_1%3A188.8.131.52-1ubuntu1.1_BUILDING.txt.gz
And if you search the log for "./configure", you'll find this:
PATH=$PATH:/build/buildd/asterisk-184.108.40.206/debian/dummyprogs ./configure \
--host=x86_64-linux-gnu --build=x86_64-linux-gnu \