The code signature version is no longer supported

codesign --generate-entitlement-der

Apple has changed the codesign signature to include DER encoded entitlements in addition to the plist encoded entitlements. This additional DER encoded entitlements section is required in iOS 15 and becomes the default behavior of codesign in the latest Xcode. To use codesign on an older machines with an older version of Xcode add the --generate-entitlement-der flag to your call to codesign.

If signing through Xcode, you can add this flag to the OTHER_CODE_SIGN_FLAGS setting in the Build Settings tab.

If codesigning at the command-line:

CODESIGN_ALLOCATE=$( xcrun --find codesign_allocate ); export CODESIGN_ALLOCATE
xcrun codesign --generate-entitlement-der ...

The source of this information was the Apple Forum thread and the answer from Matt Eaton in DTS at Apple.

In the Xcode 12.5 Release Notes there is also a reference to the new signature format. However, it seems the information is not entirely correct.

Here are some visual directions to @CameronLowellPalmer's answer.

I got the steps from @WayneHenderson's comment underneath the accepted answer.

Follow the red arrows steps 1 - 11 (there is no 8, I made a mistake and went from 7 straight to 9).

The most important thing is step 4, make sure to select All or you won't find the Other Code Signing Flags options.

For step 5 just enter Other Code Signing Flags into the search container.

Steps 9 - 11 is where you enter --generate-entitlement-der

You will need to add the --generate-entitlement-der to your OTHER_CODE_SIGN_FLAGS under Build Settings.