Move javac_wrapper.sh scripts into own files.

I have originally created those snippets as minimal
change from the previous bash-functions.

On second thought, rather than generate those files,
it is cleaner to just create those files in source.

The build script will use "javac_wrapper.sh" if it exists.

Test: check that generated run-test data is unchanged
Change-Id: Ibd0d92cf399c3026be127ac42b513382c04142f7