xcode-select is missing from /usr/bin. Try installing XCode again, and making sure you choose to install the optional Unix support and the Developer Tools System.
xcode-select is a program which should be in usr/bin that manages the path to XCode if you have multiple XCode versions installed. Versions of tools such as xcodebuild in /usr/bin are just shims that redirect to which ever version of XCode you are choosing to use.
See this Apple link and this man page. In particular, note this: "When writing software that uses the Xcode UNIX tools, Apple recommends using the copy of those tools installed in Xcode/usr instead of /usr, because your users may not have tools in /usr if they have disabled the optional UNIX Development Support choice in the Xcode installer. Your software can find the path to the directory with the xcode-select command (see previous section)."