Make references to //third_party/icu relative

This allows the build of ICU to be placed in directories other
than //third_party/icu downstream.

The change does not make a difference in code bases that
continue to use //third_party/icu.

Bug: fuchsia:108544
Change-Id: If702e4294aba6fcd45f8691a9b87cade5b4b33d2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/deps/icu/+/3868531
Reviewed-by: Jungshik Shin <jshin@chromium.org>
Reviewed-by: Frank Tang <ftang@chromium.org>
1 file changed