ci: freebsd repartition script didn't copy .git directory

We need a slightly different "cp" incantation to make sure top-level
"dot" files, such as ".git", are also copied.

This is relevant for example if a script wants to execute a git
command.  This currently does not happen, but it has come up while
testing other patches.

Reviewed-by: Tristan Partin <tristan@neon.tech>
Discussion: https://www.postgresql.org/message-id/flat/40e80f77-a294-4f29-a16f-e21bc7bc75fc%40eisentraut.org

src/tools/ci/gcp_freebsd_repartition.sh

@@ -23,4 +23,4 @@ du -hs $CIRRUS_WORKING_DIR
 mv $CIRRUS_WORKING_DIR $CIRRUS_WORKING_DIR.orig
 mkdir $CIRRUS_WORKING_DIR
 mount -o noatime /dev/md1 $CIRRUS_WORKING_DIR
-cp -r $CIRRUS_WORKING_DIR.orig/* $CIRRUS_WORKING_DIR/
+cp -a $CIRRUS_WORKING_DIR.orig/ $CIRRUS_WORKING_DIR/