The symbol currently defined in the generated assembly does not match
what the linker expects.

Also remove the outdated special case for is_win.

R=jshin@chromium.org

Bug: chromium:938223
Change-Id: I2c2d3a16df7fa7f6801d70cdf4a80e99e2572f2f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/deps/icu/+/1599430


Reviewed-by: Jungshik Shin <jshin@chromium.org>