OSX brew failing to update.

I've searched the related questions and the solutions here this site and they have not helped me remedy the situation. I've had brew installed awhile now (since 2013) and had previously been updating without incident. I'm running El Capitan 10.11.6 $ brew --version `Homebrew 0.9.5 (no git repository) ` Here's what's happening: $ brew update results in the following error output `xcrun: error: invalid active developer path (/Library/Developer/CommandLineTools), missing xcrun at: /Library/Developer/CommandLineTools/usr/bin/xcrun Error: Failure while executing: git status --untracked-files=all --porcelain 2>/dev/null`