Hello.
Problem is solved by using xwiki's maven version (
http://xwiki.org/maven-2.1-SNAPSHOT.zip )
So I think new maven-2.1-SNAPSHOT has a bug.
I'm sorry for don't try xwiki's maven earlier.
Artem Melentyev wrote:
  I have a strange bug then building
xwiki-enterprise-database by maven2
 indirectly (by pom <modules>):
 $ cd xwiki-product-enterprise
 $ mvn clean; mvn install
 result:
 database files in xwiki-product-enterprise/target/database but not in
  xwiki-product-enterprise/database/target/database
 so xwiki-enterprise-database-1.1-SNAPSHOT-hsqldb.zip is empty
 ... 
--
  Artem Melentyev, UralSU