Boot time of B2Qt is really long with Qt 5.10

Boot time of B2Qt is really long with Qt 5.10. This is because QRandomGenerator now uses getentropy which blocks during boot until kernel outputs message "random: nonblocking pool is initialized".

At least qdbd and qtlauncher are affected by this.

Possible solutions:

1. Disable feature "getentropy" from Boot2Qt builds
   • This is the behavior in Qt < 5.10.x
   • Only difference in the entropy of randomness is in early boot
2. Add "rng-tools" for inputting entropy to the kernel
   • Speeds up initialization of nonblocking pool
   • On devices with HW random generator, this adds real entropy to the kernel pool
   • On devices without HW random generator, this adds entropy from /dev/urandom to the kernel pool
3. Setting  QT_HASH_SEED for the affected processes
   • export QT_HASH_SEED=0
   • export QT_HASH_SEED=`dd if=/dev/urandom bs=1 count=4 2>/dev/null | hexdump -v -e '1/1 "%u"'`
4. Something else...

Some discussion about the issue is in comments of QTBUG-63029