Build.sh: clarify the parameter order of uptodate()

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Build.sh: Make sure that maven-helper.sh is updated properly

The 'test a"$something" = aBLUB' trick to avoid comparing something
that looks like an option to test(1) is not even needed here. But
since we use it, we might just as well implement it properly.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>