./debian/rules binary: How clear cache?

[Stef Hoesli Wiederwald <debian@sos.ethz.ch>]

I wanted to build mutt_0.95.1 from the source package. Since gettext
was not installed, it failed. (How can I find out on which packages a
source package depends anyway?) After I installed the gettext package,
I tried again. But when it is cheking for needed programs it says:

checking for msgfmt... (cached) no

But msgfmt is there now! Where is this message chached? (I deleted
mutt-0.95.1/, did dpkg-source -x mutt_0.95.1-1.dsc, cd mutt-0.95.1/
and ./debian/rules binary again, but it didn't help)
How do I empty this cache or force a check for the programs?

Stef