Disable clamav on ppc64.

Clamav support doesn't work on ppc64 due to
https://bugzilla.redhat.com/show_bug.cgi?id=1534071 so disable it there.

cyrus-imapd.spec

@@ -232,13 +232,14 @@ make
 popd
 %endif
 
-# Options not enabled:
+# Notes about configure options:
 # --enable-objectstore
 #   It's experimental, and it doesn't appear that either openio or caringo are
 #   in Fedora.
-# --with-mysql
-#   libmysqlclient doesn't support openssl 1.1 and you can't two versions of
-#   openssl linked into the same program.
+
+# --without-clamav (on ppc64 only)
+#   cyr_virusscan fails with internal llvm errors on ppc64 _only_.  See
+#   https://bugzilla.redhat.com/show_bug.cgi?id=1534071
 
 # --with-cyrus-prefix and --with-service-path went away; use --with-libexecdir=
 # instead.
@@ -270,6 +271,9 @@ autoreconf -vi
     --enable-replication \
     --enable-unit-tests \
     --enable-xapian \
+%ifarch ppc64
+    --without-clamav \
+%endif
 #
 
 # The configure script will set up the Perl makefiles, but not in the way
@@ -634,6 +638,8 @@ getent passwd cyrus >/dev/null || /usr/sbin/useradd -c "Cyrus IMAP Server" -d /v
 %changelog
 * Tue Jan 09 2018 Jason L Tibbitts III <tibbs@math.uh.edu> - 3.0.5-3
 - Re-enable clamav and mariadb support as those are now built with openssl 1.1.
+- But no clamav on ppc64 because of
+  https://bugzilla.redhat.com/show_bug.cgi?id=1534071
 
 * Thu Jan 04 2018 Jason L Tibbitts III <tibbs@math.uh.edu> - 3.0.5-2
 - Reorganize some test exclusions so things build on all releases.