Building on Gentoo

I am attempting to use FreeTDS on Gentoo to make a "Trusted Connection" 
to MS SQL Server. To that end, I believe I need both Kerberos support 
and SSPI support. To isolate the problem, I have down loaded the 
tarball, and I am compiling manually outside of the Gentoo build system. 
I am using the following  ./configure line generated by Gentoo. Note the 
--enable-sspi flag:

  ./configure --prefix=/usr --build=x86_64-pc-linux-gnu 
--host=x86_64-pc-linux-gnu --mandir=/usr/share/man 
--infodir=/usr/share/info --datadir=/usr/share --sysconfdir=/etc 
--localstatedir=/var/lib --libdir=/usr/lib64 
--disable-dependency-tracking --with-tdsver=7.0 --enable-msdblib 
--enable-odbc --with-unixodbc=/usr --enable-krb5 --enable-sspi

Yet when I run the resulting binary, I get this:

  src/apps/tsql -C
Compile-time settings (established with the "configure" script)
                             Version: freetds v0.91
              freetds.conf directory: /etc
      MS db-lib source compatibility: yes
         Sybase binary compatibility: no
                       Thread safety: yes
                       iconv library: yes
                         TDS version: 7.0
                               iODBC: no
                            unixodbc: yes
               SSPI "trusted" logins: no
                            Kerberos: yes

Is this build option only available on Windows perhaps?

Thanks,

Spencer