development/apache-maven: Allow VERSION override.

Signed-off-by: B. Watson <yalhcru@gmail.com>
Signed-off-by: David Spencer <idlemoor@slackbuilds.org>

development/apache-maven/apache-maven.SlackBuild

@@ -24,7 +24,7 @@
 # ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 PRGNAM=apache-maven
-VERSION=3.3.9
+VERSION=${VERSION:-3.3.9}
 ARCH=noarch
 BUILD=${BUILD:-1}
 TAG=${TAG:-_SBo}