Use SCM_FILE_LINKS properly and some cleanups of report test makefiles

- Only some files need to be linked into a virtual guile module dir
  The others should be linked into the build dir if building out of tree
- Drop the .sh extension from test wrappers
- Move makefile variables and targets around a bit to be more consistent in the two makefiles

git-svn-id: svn+ssh://svn.gnucash.org/repo/gnucash/trunk@23036 57a11ea4-9604-0410-9ed3-97b8803252fd