Merge branch 'hotfix/1.18.15' into stable
1.18.16
make sure 1.9/2.0 MRI is picked for compiling rbx, fix #1596, includes parts of ee92d0d402525feacbfbbb2817d3116234e9a700
Merge branch 'hotfix/1.18.16'

Conflicts:
	scripts/functions/build
	scripts/functions/manage/rubinius
	scripts/functions/manage/ruby