Why is rolemap m4 expanded

[Joe Nall <joe nall com>]

/usr/share/selinux/devel/include/rolemap looks like this for a default  
selinux-policy-3.5.10 install (minus the comments):

user_r user user_t
staff_r staff staff_t
sysadm_r sysadm sysadm_t

The rolemap in the source rpm looks like:

user_r user user_t
staff_r staff staff_t
sysadm_r sysadm sysadm_t

ifdef(`enable_mls',`
        secadm_r secadm secadm_t
        auditadm_r auditadm auditadm_t
')

The enable_mls clause is lost in the installation m4 expansion. Why is  
this file m4 processed on installation?

joe