build(update.sh): Don't always perform the expensive `upgrade`

update.sh

@@ -19,9 +19,14 @@
 # and the Lesser GNU General Public License along with this program.
 # If not, see <https://www.gnu.org/licenses/>.
 
-cargo update && cargo upgrade
+update() {
+    [ "$1" = "upgrade" ] && cargo upgrade
+    cargo update
+}
+
+update "$@"
 cd ./example/main || {
     echo "Main example is missing"
     exit 1
 }
-cargo update && cargo upgrade
+update "$@"