Allow 'icupkg' to build data package without dependency check.

This is needed to split icu data resources into multiple
files without requiring root.res to be present in all of them.

https://unicode-org.atlassian.net/browse/ICU-20774


Bug: chromium:969181
Change-Id: I7b397b95bfd691cc07e4f04a05bf54d691fd5995
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/deps/icu/+/1754515
Reviewed-by: Jungshik Shin <jshin@chromium.org>
3 files changed