qbs build: Make the autotest template available as an import.

Just like for QtcPlugin, QtcLibrary etc.

Change-Id: I395f5863f31abba589864be3ad41ad7fc893787f
Reviewed-by: Jake Petroules <jake.petroules@petroules.com>
Fix qbs build with clang.

Properties item considered harmful.

Change-Id: I715b589bdcb6ef9ac35790122a1ba6f009652242
Reviewed-by: Joerg Bornemann <joerg.bornemann@digia.com>