Install links for zpool feature compat aliases

The alias links were missed when this feature was introduced to the
FreeBSD build system in 10f57cb9.

Reviewed by:	mm
Sponsored by:	iXsystems, Inc.
Differential Revision:	https://reviews.freebsd.org/D28925

(cherry picked from commit 2ae79aa3)

cddl/share/zfs/compatibility.d/Makefile

@@ -25,4 +25,25 @@ FILES= \
 
 FILESDIR= ${SHAREDIR}/zfs/compatibility.d
 
+LINKS= \
+	${FILESDIR}/compat-2018		${FILESDIR}/2018 \
+	${FILESDIR}/compat-2019		${FILESDIR}/2019 \
+	${FILESDIR}/compat-2020		${FILESDIR}/2020 \
+	${FILESDIR}/compat-2021		${FILESDIR}/2021 \
+	${FILESDIR}/freebsd-11.0	${FILESDIR}/freebsd-11.1 \
+	${FILESDIR}/freebsd-11.0	${FILESDIR}/freenas-11.0 \
+	${FILESDIR}/freebsd-11.2	${FILESDIR}/freenas-11.2 \
+	${FILESDIR}/freebsd-11.3	${FILESDIR}/freebsd-11.4 \
+	${FILESDIR}/freebsd-11.3	${FILESDIR}/freebsd-12.0 \
+	${FILESDIR}/freebsd-11.3	${FILESDIR}/freebsd-12.1 \
+	${FILESDIR}/freebsd-11.3	${FILESDIR}/freebsd-12.2 \
+	${FILESDIR}/freebsd-11.3	${FILESDIR}/freenas-11.3 \
+	${FILESDIR}/freenas-11.0	${FILESDIR}/freenas-11.1 \
+	${FILESDIR}/openzfsonosx-1.9.3	${FILESDIR}/openzfsonosx-1.9.4 \
+	${FILESDIR}/openzfs-2.0-freebsd	${FILESDIR}/truenas-12.0 \
+	${FILESDIR}/zol-0.7		${FILESDIR}/ubuntu-18.04 \
+	${FILESDIR}/zol-0.8		${FILESDIR}/ubuntu-20.04
+
+LINKMODE= ${NOBINMODE}
+
 .include <bsd.prog.mk>