Hi Carlton,

I can't offer any guarantees for QNX 6.5, but I can pass along the patch we use for MIT krb5 to build for QNX 6.6.   It 
may not work out of the box but hopefully it'll give you a leg up.   Our build system is derived from Arch Linux's 
makepkg, so the build instruction we use were originally sourced from https://github.com/archlinux/svntogit-packages/
tree/packages/krb5/trunk .    Our system is currently building krb5 version 1.19.1 and requires libldap (from openldap) 
to be available in the environment.

----

# Build environment
CARCH="ntox86"
CHOST="x86-unknown-nto-qnx"
CBUILD="x86_64-unknown-linux-gnu"
export CC=qcc
export CXX=QCC
export CFLAGS="-O2"
export AR="${CARCH}-ar"
export AS="${CARCH}-as"
export ELFEDIT="${CARCH}-elfedit"
export LD="${CARCH}-ld"
export NM="${CARCH}-nm"
export OBJDUMP="${CARCH}-objdump"
export OBJCOPY="${CARCH}-objcopy"
export RANLIB="${CARCH}-ranlib"
export SIZE="${CARCH}-size"
export STRINGS="${CARCH}-strings"
export STRIP="${CARCH}-strip"


# Config overrides
export CFLAGS+=" -fno-strict-aliasing -fstack-protector-all"
export krb5_cv_attr_constructor_destructor=yes,yes
export ac_cv_func_regcomp=no
export ac_cv_printf_positional=no

# Prepare sources
# cf https://bugs.gentoo.org/show_bug.cgi?id=448778
patch -Np1 < krb5-config_LDFLAGS.patch
# QNX cross-build fixes
patch -Np1 < qnx-port.patch
# FS#25384
sed -i "/KRB5ROOT=/s/\/local//" src/util/ac_check_krb5.m4

# Configure and build
./configure --build=${CBUILD} --host=${CHOST} \
            --prefix=/usr \
            --sbindir=/usr/bin \
            --sysconfdir=/etc \
            --localstatedir=/var/lib \
            --enable-shared \
            --disable-rpath \
            --without-tcl \
            --enable-dns-for-realm \
            --with-ldap \
            --without-system-verto
               
make

----

I hope this is of some help.  Good luck!

-Will