IF someone tries to use security/krb5 to stay MIT or security/heimdal to get a newer version of heimdal postgresql is one of packages that wouldn't work anymore out of the box.

So we have:

1. World WITHOUT_KERBEROS and WITHOUT_KERBEROS_SUPPORT.
2. Trying to build postgresql server.

Here we go down:

configure:3851: $? = 1
configure:3871: checking whether the C compiler works
configure:3893: clang60 -O3 -pipe -march=native  -O3 -funroll-loops -fstack-protector -fno-strict-aliasing -I/usr/local/include  -L/usr/local/lib -lpthread -lgssapi -L/usr/local/lib -Wl,-rpath,/usr/local/lib -fstack-protector conftest.c  > &5
/usr/local/bin/ld: cannot find -lgssapi

This happens because:

 - security/krb5 provides libgssapi_krb5 in /usr/local/lib (missed);
 - security/heimdal provides libgssapi in /usr/local/lib/heimdal (not included in -L)

Here's an example how this can be solved (I'm not good with options so this is just to show the concept):

OPTIONS_RADIO+=         GSSAPI
OPTIONS_RADIO_GSSAPI= GSSAPI_HEIMDAL GSSAPI_MIT
.if exists(/usr/lib/libgssapi.so) # ? didn't have it installed
OPTIONS_RADIO_GSSAPI+= GSSAPI_BASE
OPTIONS_DEFAULT+=      GSSAPI_BASE
GSSAPI_BASE_USES=              gssapi:base
GSSAPI_BASE_CONFIGURE_ON=      --with-gssapi
.endif

GSSAPI_HEIMDAL_USES=           gssapi:heimdal,flags
GSSAPI_HEIMDAL_CONFIGURE_ON=   --with-gssapi
GSSAPI_HEIMDAL_CFLAGS+=        -I/usr/local/include/heimdal
GSSAPI_HEIMDAL_LDLAGS+=        -L/usr/local/lib/heimdal
GSSAPI_HEIMDAL_LIB_DEPENDS+=   libgssapi.so:security/heimdal

GSSAPI_MIT_USES=               gssapi:mit
GSSAPI_MIT_CONFIGURE_ON=       --with-gssapi
GSSAPI_MIT_CFLAGS+=            -I/usr/local/include
GSSAPI_MIT_LDLAGS+=            -L/usr/local/lib
GSSAPI_MIT_LIB_DEPENDS+=       libgssapi_krb5.so:security/krb5
.endif

Hope this helps a little.