Revert "[config] Declare the args conditionally"

This reverts commit b6d6790dc9f575a8c48daa94190b59cbf1342bce.

Reason for revert: This also wasn't the correct approach, 
similar to https://chromium-review.googlesource.com/c/chromium/deps/icu/+/4118185.

Original change's description:
> [config] Declare the args conditionally
>
> Fuchsia compiles several flavors of ICU at once, and
> each brings in its own declare_args.  This makes all
> such compilations use the same args values, without
> breaking the build.
>
> Bug: fuchsia:116006
> Change-Id: Ib2f8fd98e1b4f45f036f698dcf66a2255f898af4
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/deps/icu/+/4054140
> Reviewed-by: Frank Tang <ftang@chromium.org>

Bug: fuchsia:116006
Change-Id: Ibd920b33c62c8d7ae4e3731427f12e50c9542da3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/deps/icu/+/4118186
Reviewed-by: Jungshik Shin <jshin@chromium.org>
1 file changed