Homebrew on macOS 10.13, what's the best way to update?

Question

macOS

So we have macOS 10.13 and brew 0.9.9. A number of packages have been installed via brew.
The catch is that the current version of brew does not support the current version of os.

brew upgrade
Warning: You are using OS X 10.13.
We do not provide support for this pre-release version.
You may encounter build failures or other breakages.

brew does not want to update, as the first thing it swears about is the lack of write permissions to /usr/local

brew update
Error: /usr/local must be writable!

chown will not work, since the directory is protected by System Integrity Protection, therefore, you need to disable it, change the rights to the folder and try to update it again.
However, I have doubts whether I'm thinking correctly and whether I'm going the right way, because I don't want to disable SIP.
Is the problem only in the rights to the folder or will there be another trail of problems later? If that's the case, then maybe there's an easier solution that I don't know about, like reinstalling brew. (Unfortunately, I don’t know if it is removed along with the installed packages or not, if there are problems with accessing the directory when reinstalling, etc.)
Share who faced this problem and how they solved it.

Answer 1

new versions of brew do not require disabling vulture.
just turn off sip, update brew, turn sip back on.
as an option - make a backup of the system and just try to roll a fresh bru from above.