deps: port ICU ClangCL fix

This is a change I landed in the ICU at https://github.com/unicode-org/icu/pull/3023. It is needed to enable ClangCL compilation for Node.js on Windows and that's why I'm porting it manually now before the next ICU update. After this PR lands, I'll open a follow-up one changing the icu-generic.gyp to take advantage of the ICU changes.

cc @targos @nodejs/platform-windows