QRandomGenerator only returns zeros on Linux

This is a follow-up to QTBUG-69423, and based on the diagnostics program (hwtest.cpp) posted in that bug.

The program is failing on a XenServer VM, where QRandomGenerator::system() returns a bunch of zeros rather than random values. However, reading the output of /dev/urandom on a shell gives us random values.

This the output of the program (compiled with Clang):

Compile-time features:
 - GCC-compatible compiler version 402
 - Compiler supports RDRND instruction set
Runtime CPU features:
 - Maximum basic CPUID leaf 13
 - CPUID leaf 1 ECX = 0xc3ba2203
 - CPU doesn't have RDRND support
Dumping 64 bytes from QRandomGenerator::system() (should be zeroes):
 0x0 0x0 0x0 0x0 0x0 0x0 0x0 0x0 0x0 0x0 0x0 0x0 0x0 0x0 0x0 0x0
Samples from QRandomGenerator::system():
 0x0 0x0 0x0 0x0 0x0 0x0 0x0 0x0 0x0 0x0
Samples from the HW generator (this may crash):
 (0 entries total)
 0x0 0x0 0x0 0x0 0x0 0x0 0x0 0x0 0x0 0x0

The output of strace has been attached. I guess the relevant line is:
getrandom(0x7fffd88a0060, 40, 0) = -1 ENOSYS (Function not implemented)
I suppose the issue here is that while our Docker VM runs a recent Ubuntu, the Docker host is Debian Jessie. Jessie comes with kernel 3.16, while getrandom was only implemented in kernel 3.17. I couldn't find any information on Qt requiring a specific kernel version.