Add gentoo linux

README.md

@@ -36,6 +36,7 @@ Wiki: https://github.com/Neilpang/acme.sh/wiki
 |16|[![](https://cdn.rawgit.com/Neilpang/acmetest/master/status/mageia.svg)](https://github.com/Neilpang/letest#here-are-the-latest-status)|Mageia
 |17|-----| OpenWRT: Tested and working. See [wiki page](https://github.com/Neilpang/acme.sh/wiki/How-to-run-on-OpenWRT)
 |18|[![](https://cdn.rawgit.com/Neilpang/acmetest/master/status/solaris.svg)](https://github.com/Neilpang/letest#here-are-the-latest-status)|SunOS/Solaris
+|18|[![](https://cdn.rawgit.com/Neilpang/acmetest/master/status/gentoo-stage3-amd64.svg)](https://github.com/Neilpang/letest#here-are-the-latest-status)|Gentoo Linux
 
 For all build statuses, check our [daily build project](https://github.com/Neilpang/acmetest):