The includes -I${KRB5DIR}/lib/krb5 -I${KRB5OBJDIR} -I${ASN1OBJDIR} are incorrect and not used. See example below. It is proposed that the include directory specifications be removed.
cc -target x86_64-unknown-freebsd12.0 --sysroot=/usr/obj/export/home/cy/freebsd/svn/current/tmp -B/usr/obj/export/home/cy/freebsd/svn/current/tmp/usr/bin -O2 -pipe -pipe -I/export/home/cy/freeb
sd/svn/current/contrib/telnet -DENCRYPTION -DAUTHENTICATION -DSRA -DKRB5 * SEE HERE ---> -I/lib/krb5 -I -I <--- * -DFORWARD -Dnet_write=telnet_net_write -MD -MF.depend.genget.o -MTgenget.o -std=gnu99 -fstack-protector-
strong -Wsystem-headers -Werror -Wall -Wno-format-y2k -Wno-uninitialized -Wno-pointer-sign -Wno-empty-body -Wno-string-plus-int -Wno-unused-const-variable -Wno-tautological-compare -Wno-unused-val
ue -Wno-parentheses-equality -Wno-unused-function -Wno-enum-conversion -Wno-unused-local-typedef -Wno-address-of-packed-member -Wno-switch -Wno-switch-enum -Wno-knr-promoted-parameter -Qunused-ar
guments -c /export/home/cy/freebsd/svn/current/contrib/telnet/libtelnet/genget.c -o genget.o