After updating to Catalina, all was fine until I loaded the most recent update.
Then I had to migrate my licence for Xojo. After doing that, I built my app and tried to wrap it with apoWrapper.
I got the following message.
codesign: /Users/phil/Library/Caches/com.ohanaware.appWrapper3/App Wrapper 3: replacing existing signature
xcrun: error: invalid active developer path (/Library/Developer/CommandLineTools), missing xcrun at: /Library/Developer/CommandLineTools/usr/bin/xcrun
/Users/phil/Library/Caches/com.ohanaware.appWrapper3/App Wrapper 3: the codesign_allocate helper tool cannot be found or used
macOS 10.15.1 (19B88)
App Wrapper 3 3.10.2 (359)
Sam fro Ihanaware sent me a new build of AppErapper, but I still had the same problem.
I went looking for answers on https://apple.stackexchange.com/questions/209624/how-to-fix-homebrew-error-invalid-active-developer-path-after-upgrade-to-os-x
They recommended using a terminal to run:
sudo xcode-select --install
sudo xcode-select -switch
I ran these commands one after the other in terminal, and despite the system telling me that they had not been installed, I was now able to use appWrappee to wrap my application, code sign and install it.
Hope that helps someone else with the same problem.