Remove MK_GSSAPI

For MIT Kerberos, MK_GSSAPI has no meaning: GSSAPI is a required part of
Kerberos and is always built if MK_KERBEROS is enabled.  Backport this
behaviour to Heimdal so it works the same way.

While here, change Heimdal's libcom_err and compile_et to be selected by
MK_KERBEROS, not MK_KERBEROS_SUPPORT, since these are part of Kerberos
and third-party users might need it even if Kerberos support is disabled
in the base system.  This means MK_KERBEROS_SUPPORT installs the same
files with both MIT and Heimdal.

Reviewed by:	cy
Differential Revision:	https://reviews.freebsd.org/D51859

kerberos5/Makefile.inc

@@ -29,9 +29,7 @@ ETSRCS=	\
 	${KRB5DIR}/lib/wind/wind_err.et \
 	${KRB5DIR}/lib/ntlm/ntlm_err.et
 
-.if ${MK_GSSAPI} != "no"
 ETSRCS+=	${KRB5DIR}/lib/gssapi/krb5/gkrb5_err.et
-.endif
 
 .for ET in ${ETSRCS}
 .for _ET in ${ET:T:R}

kerberos5/lib/Makefile

@@ -7,10 +7,8 @@ SUBDIR=	libasn1 libhdb \
 SUBDIR+= libkafs5  # requires krb_err.h from libkrb5
 SUBDIR_DEPEND_libkafs5=	libkrb5
 
-.if ${MK_GSSAPI} != "no"
 SUBDIR+=	libgssapi_krb5
 SUBDIR+=	libgssapi_ntlm
 SUBDIR+=	libgssapi_spnego
-.endif
 
 .include <bsd.subdir.mk>

kerberos5/libexec/Makefile

@@ -4,8 +4,6 @@ SUBDIR=	digest-service ipropd-master ipropd-slave hprop hpropd kdc \
 	kdigest kfd kimpersonate kpasswdd kcm
 SUBDIR_PARALLEL=
 
-.if ${MK_GSSAPI} != "no"
 SUBDIR+=	kadmind
-.endif
 
 .include <bsd.subdir.mk>