macos - Homebrew doesn't install new apps in El Capitan

just upgraded to beta El Capitan for developers.

Deniss-MBP:src me$ brew install hg
Warning: You are using OS X 10.11.
We do not provide support for this pre-release version.
You may encounter build failures or other breakage.
==> Downloading https://mercurial.selenic.com/release/mercurial-3.4.2.tar.gz
Already downloaded: /Library/Caches/Homebrew/mercurial-3.4.2.tar.gz
==> make PREFIX=/usr/local/Cellar/mercurial/3.4.2 install-bin
#include 
         ^
1 error generated.
error: command 'clang' failed with exit status 1
make: *** [build] Error 1

READ THIS: https://git.io/brew-troubleshooting

Warning: You are using OS X 10.11.
We do not provide support for this pre-release version.
You may encounter build failures or other breakage.

Any ideas how to make it work?

Note: When I do brew doctor it says

Warning: Your Xcode (6.3.2) is outdated
Please update to Xcode 7.0.
Xcode can be updated from
  https://developer.apple.com/downloads

But I do have xcode-beta 7 installed on my computer. Not sure this is linked. Just in case

Answer

First I recommend you go over this: https://www.reddit.com/r/apple/comments/3994os/rootless_feature_is_in_os_x_1011_and_it_disallows/

The rootless security changed a lot of things in El Capitan, other than that where does your xcode-select point to? You can use xcode-select -h to see the usage, it's very simple.