If any other site links to your site, Google (and all the other search engines) will find out about it.
If no one links to your site, it doesn't matter, because a site with no links to it isn't going to rank very high in the search engine results pages (SERPS).
Now, before you ask "So how do I get my site to rank high", that's what half the millions of posts on this forum are about. Start doing some reading. Good luck. :)