fix openjdk build error: Prefix import missing (#23014)

fixes #23013

var/spack/repos/builtin/packages/openjdk/package.py

@@ -7,6 +7,7 @@
 import platform
 import re
 
+from spack.util.prefix import Prefix
 
 # If you need to add a new version, please be aware that:
 #  - versions in the following dict are automatically added to the package