Chroot replay

This patch aims to partially solve the replay problem via chroot jail.

Currently `klee-replay` doesn't have any protection against dangerous test cases such as `rm -rf /`. This patch adds a call to `chroot` before the program under test is `execv`ed, thus creating a jail for the program under test. We only need to grant `SYS_CAP_CHROOT` to `klee-replay` to accomplish its job. 

A simple script for building the chroot environment is also provided. It analyze a program's shared library dependency by calling `ldd` and copies them to the sandbox path.