Add fix for failing ICU download url

[ccasey645]

Add updated ICU download URL after ICU dependency's tgz file was migrated from Subversion repo to GitHub repo (source: http://site.icu-project.org/repository).

Purpose: Meta's cmake steps will fail to download the ICU dependency because the old URL for the ICU dependency does not have the Tar file anymore. Without this updated URL that has the ICU dependency Meta needs to build, no-one can make builds of Meta.

[GasolSun36]

i am sorry ,i can't find any CMakeList.txt file have this FindOrBuildICU( VERSION 63.1 URL http://download.icu-project.org/files/icu4c/63.1/icu4c-63_1-src.tgz URL https://github.com/unicode-org/icu/releases/download/release-63-1/icu4c-63_1-src.tgz URL_HASH SHA512=9ab407ed840a00cdda7470dcc4c40299a125ad246ae4d019c4b1ede54781157fd63af015a8228cd95dbc47e4d15a0932b2c657489046a19788e5e8266eac079c ) i am a little bit confused,please tell how to solve this problem!