Make it able to optionally disable thin_archive

To compile libicu into static library, we need to disable
"thin_archive" to make it standalone.

BUG=chromium:1020393
TEST=on workstation, this mod can produce usable libicu*.a

Change-Id: I16420b4bbab7e27d6170406ef2c577baa539e5f1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/deps/icu/+/2063614
Reviewed-by: Jungshik Shin <jshin@chromium.org>