merge revision(s) 9f708d48, 0301473f, 874e9fc3, 7f0e26b7: [Backport #20516]

	Clear runtime dependencies if default gems is specified.

	The current build system uses runtime dependencies from only
	`.bundle` directory. We shouldn't install runtime dependencies
	from rubygems.org when `make test-bundled-gems` is invoked.

	Fixed dependencies list format

	Don't need to remove ruby2_keywords dependency from drb

	Re-use strscan with ruby repo