Fix the ant build script (for Windows)

Ant will fail by default if a directory listed in a FileSet is not
 present... which is the case of /usr/share/java/ on Windows
/usr/share/java should also be scanned for libtest

Thanks to RdrOfTheSt0rm for pointing it out!
Uniformize the javac invocations

Specify the following options for tests too
 includeAntRuntime="false" encoding="UTF-8"