Synchronously execute command using a Bourne-compatible shell,
returns (values output error-output exit-status).

The command can be a full path to a shell executable binary
or just its name. In the later case, the variable *shell-search-paths*
will be used to find the executable.

Depending on the implementation, the variable *bourne-compatible-shell*
may be used to find a shell to use in executing command.