We already do this for `runsc run`, but need to do the same for `runsc exec`. PiperOrigin-RevId: 270793459
This can be merged after: https://github.com/google/gvisor-website/pull/77 or https://github.com/google/gvisor-website/pull/78 PiperOrigin-RevId: 253132620
runsc will now set the HOME environment variable as required by POSIX. The user's home directory is retrieved from the /etc/passwd file located on the container's file system during boot. PiperOrigin-RevId: 253120627