Hardcode path to ICU on macOS (#28066)

Port of dotnet/runtime@05f17e3.

Author: ViktorHofer

src/corefx/System.Globalization.Native/CMakeLists.txt

@@ -32,7 +32,7 @@ else()
         return()
     endif()
 
-    add_definitions(-DOSX_ICU_LIBRARY_PATH=\"${ICUCORE}\")
+    add_definitions(-DOSX_ICU_LIBRARY_PATH=\"/usr/lib/libicucore.dylib\")
 endif()
 
 include(configure.cmake)