remove support for VSC-tools, will add it later once it has stabilized
add --no-clean-on-error to R installation commands
pass zlib/ncurses lib dirs in Makefile where required
add ported easyblock for ant
add ported easyblock for JAR files (e.g. JUnit)
add dedicated easyblock for XML R package, required to set LIBS for zlib dependency
don't return result of sanity check, doesn't make sense
Revert "remove support for VSC-tools, will add it later once it has stabilized"

This reverts commit e55422bf6a48ecd3740e410e0c6ab9c2fb68c06f.