The document of 'doc/building.md' at chapter 'Rebuilding faster with build/make.sh' has a typo bug, which may cause misunderstand.
Anyone wants to skip download dependencies, the option '--skip-download' should passed to 'make/build.sh' explicitly. Because the default valune of variable 'SKIP_DOWNLOAD' in 'https://github.com/openjdk/jtreg/blob/master/make/build-support/build-common.sh#L155' is empty, unless execute 'make/build.sh' with '--skip-download'.