how should I build a pam_krb5 module?

[Ed Berger <nobody@xxxxxxxxx>]

I wanted to enable kerberos login in dragonfly-development, since 
kerberos is used at my work place, so I uncommented the krb5 related 
lines in the /etc/pam.d config files and found out the hard way that the 
pam_krb5.so module was missing...