Upgrade to Big Sur Beta 3 Broke Brew Build system Today I upgraded to Big Sur Beta3 and I cannot install anything with Brew. I get the error:
Error: Your Xcode (11.6) is too outdated.
Please update to Xcode 12.0 (or delete it).
Xcode can be updated from:
  https://developer.apple.com/download/more/

Error: Could not find an SDK that supports macOS 11.0.
You may have have an outdated or incompatible Xcode.
Homebrew found the following SDKs in the Xcode install:
  10.15

I can safely Ignore first error as I have tried everything I state here with XCode 12 Beta2 yielding the same results. The second one which is actually the issue I get seems to come from name changes that makes this Beta to be 11.0 instead of 10.16.
I have read blog post proposing setting special environment variable and I set as below but still does not work.
export SYSTEM_VERSION_COMPAT=1

Any pointer or help is appreciated
Same thing happened to me, you need to install the most recent Beta version of command line tools as well as the matching XCode 12 Beta. The same thing also happens with git and other things added by the download https://developer.apple.com/download/more/?=xcode