fix cups release

.drone.yml

@@ -7,10 +7,12 @@ steps:
     image: xoxys/rpmbuild-centos7
     user: root
     pull: always
+    environment:
+      CUPSRELEASE: "2.2.10"
     commands:
       - yum install -y gnutls-devel pam-devel dbus-devel avahi-devel systemd-devel
-      - wget https://github.com/apple/cups/releases/download/v2.2.10/cups-2.2.10-source.tar.gz
-      - rpmbuild -ta --without libusb1 cups-2.2.10-source.tar.bz2
+      - wget https://github.com/apple/cups/releases/download/v$CUPSRELEASE/cups-$CUPSRELEASE-source.tar.gz
+      - rpmbuild -ta --without libusb1 cups-$CUPSRELEASE-source.tar.gz
     when:
       event:
         - push