linux-user uses the rand function for generating the value of the AT_RANDOM elf aux vector entry, and explicitly seeds the random number generator with the current time. This makes it impossible to reproduce runs that use the AT_RANDOM bytes.
This patch adds a command line option and a matching environment variable for setting the random seed, so that the AT_RANDOM values can be predictable when the user chooses. The default is still to seed the random number generator with the current time.
