When compiling I get this:
options.c:24:18: error: popt.h: No such file or directory
The fix is here:
After changing it to #include "popt/popt.h", rsync builds.
I would suggest fixing the configure script to find out whether it will be necessary to use the "system" one or the "local" one.
(apparently on the MontaVista-based system I'm working with, the library is included but the header is not... I'm not sure why.)
Oh now I see the --with-included-popt option :-)
Anyway the configure script should be able to predict that if the header is not found, it's not going to compile. Maybe if either of the header or the lib are not found, then use the built-in version automatically.
The configure script was checking for the needed library already, but did not check if the popt.h file was in a weird place. I made it fall-back to choosing the included popt code if popt.h is in a popt subdir in the system (which avoids a potential conflict between our supplied popt/popt.h and the system's library due to our use of -I.).