`tap package verify` fails on Linux for OpenTAP and SDK

The files failing verification contain the \ path separator instead of / in the package XML description file.

When writing the unit tests and fixing the issues, a couple more problems emerged:

• a 0 exit code (to be changed to 2) was returned for inconclusive package verification because of missing file checksum information;
• tap package create crashed during the SDK package creation because of a long standing GitVersionCalulator issue on Linux.