Edit: Wow...within 20 seconds of me posting this, an update to "Command Line Tools" version 9.2 showed up in the App Store app. So, if you have this problem, check updates again.
Anyone else getting a warning about command line tools?
$ brew doctor
tells me:
Warning: A newer Command Line Tools release is available.
Update them from Software Update in the App Store.
Looking around, I see that there are two sets of the command line tools installed. There is a set in
/Library/Devloper/CommandLineTools/usr/bin
and a set in
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin
The latter is what /usr/bin/clang invokes. The /Library/Developer set is older. The file date on clang is 2017-10-20 on that one, and 2017-11-17 on the one under XCode.app.
Homebrew checks the command line tools version by running "clang --version". It uses this one:
/Library/Devloper/CommandLineTools/usr/bin/clang
It has the /Library/Developer/CommandLineTools prefix hard coded.
The version I have there is 900.0.38. The version under Xcode.app is 900.0.39.2 (which is the version Homebrew wants).
Looking back at my Time Machine backups, I see that /Library/Developer/CommandLineTools/usr did not even have a bin directory until 2017-11-23 (it just had usr/share/man). The bin directory there, and its contents, were apparently created when I installed "Command Line Tools (macOS High Sierra Version 10.13) for Xcode" version 9.1 from the App Store on 2017-11-22. That had clang version 900.0.38. That is also the version that was under Xcode.app at the time.
It looks like on 2017-12-06 there was an Xcode update (version 9.2) that updated the command line tools under Xcode.app bringing the clang version to 900.0.39.2 (which is the one Homebrew wants).
I haven't seen any updates for the "Command Line Tools" package, so what is the correct way to get the 900.0.39.2 tools into /Library/Developer/CommandLineTools/usr/bin, where Homebrew expect to find them? Is Apple just being slow to get the update out?