update buildscript
1. allow user to choose if 'out' should be used and does not exist
2. create out and subdirectories
3. Switches to shutdown aroma, checksums, ftp and prebuilts
4. update 'common-sense' variables

Signed-off-by: Dennis Rassmann <showp1984@gmail.com>
do not exit, return.

Signed-off-by: Dennis Rassmann <showp1984@gmail.com>
only copy prebuilts if the path set does actually exist

Signed-off-by: Dennis Rassmann <showp1984@gmail.com>