#634 Build failing due to JavaDoc linting under recent OpenJDK 19+ (except Ubuntu)

[Mike Clark]

Build is failing due to JavaDoc linting under recent OpenJDK 19+ (except Ubuntu). This patch is on one file, build.xml:

• disables JavaDoc linting in build.xml
• moved the core of target generate-javadoc to a new target nodeps-generate-javadoc. This new target can be run standalone (after compiling) which makes it faster to iterate on testing changes to the JavaDoc (in case someone wants to take on fixing the JavaDoc lint errors).
• generate-javadoc now <antcall>s nodeps-generate-javadoc where it used to contain the logic inline
• the core compile classpath is now pulled from a globally defined path id, instead of defining the path inside the target. compile was always creating a globally referenceable path id, but that's inconvenient if you want to run or write a target that doesn't call compile.