Installing system Ruby should check permissions before compiling

[rennex]

I used ruby-install --system --latest ruby, and after some minutes of compilation, it failed:

Permission denied @ rb_sysopen - /usr/local/share/man/man1/ruby.1 (Errno::EACCES)

Without digging too deep, I assume this happened because I didn't use sudo. Running the command again with sudo succeeded, but it meant downloading the tarball again and waiting for the recompilation. Maybe there was a way to resume the previous attempt, but finding that out from docs would've taken longer :)

So I would suggest checking in the beginning if sudo will be needed and hasn't been used, before spending time doing lots of work. Or alternatively, let the user enter their password into sudo when that's needed.