Shell built-in command detection?

[Andrew Begel]

I'm using Autoconf 2.52, and trying to detect the shell command, printf 
using

AC_CHECK_PROG(PRINTF, printf, printf)

This check comes up empty when printf is not a standalone binary, but a 
built-in shell command (on bash in MSYS/Windows it is). What is the 
proper check to use in this case?

Thanks,

Andrew