* sim-options.c (STANDARD_OPTIONS): New member OPTION_SYSROOT.
(standard_options): Support --sysroot=<path>.
(standard_option_handler): Handle OPTION_SYSROOT.
* syscall.c (simulator_sysroot): Define, initialized empty.
(get_path): Prepend simulator_sysroot to absolute file path.
[HAVE_STRING_H]: Include string.h.
[!HAVE_STRING_H && HAVE_STRINGS_H]: Include strings.h.
* nrun.c [HAVE_UNISTD_H]: Include unistd.h.
(main): If simulator_sysroot is not empty, chdir there.
* sim-config.h (simulator_sysroot): Declare.
