I upgraded my laptop to macOS Monterey, then some command-line dev things broke with errors, including these:

clang: error: invalid version number in '-mmacosx-version-min=12.3'

cc: error: unable to read SDK settings for '/Library/Developer/CommandLineTools/SDKs/MacOSX10.12.sdk'

It was a simple matter of updating Xcode (why didn’t Monterey do that?):

% sudo rm -rf /Library/Developer/CommandLineTools
% sudo xcode-select --install
% sudo xcode-select --switch /Library/Developer/CommandLineTools

I might not have needed to do all of that, but it was easy enough to start fresh. The last bit updated the default path for Monterey, which apparently is different than before.