New sh_string implementation breaks on Android 5 Lollipop (ksh)

[zachriggle]

Unfortunately, printf is not universal. It is missing from the toolbox implementation of ksh.

root@generic:/ # echo hello
hello
root@generic:/ # echo -e "h\x65llo"
hello
root@generic:/ # printf hello
/system/bin/sh: printf: not found

It seems that a non-universal solution is needed for this.

Linux is easy.

The BSDs make it hard, but we can detect those scenarios with context.os='freebsd' or similar.

Android will require active detection of the current device and its capabilities.

The implementation was changed in 72207cf. It's not clear whether it ever worked on Android, but the current implementation definitely does not.

[zachriggle]

This is now fixed via #717. The specific use of echo is broken, because echo is broken.