Add the same flag that we added to Package.swift to cmakefile

Author: itingliu

CMakeLists.txt

@@ -52,7 +52,9 @@ add_compile_definitions(
     $<$<COMPILE_LANGUAGE:C,CXX>:U_IO_IMPLEMENTATION>
     $<$<COMPILE_LANGUAGE:C,CXX>:ICU_DATA_DIR="/usr/share/icu">
     $<$<COMPILE_LANGUAGE:C,CXX>:USE_PACKAGE_DATA=1>
-    $<$<COMPILE_LANGUAGE:C,CXX>:APPLE_ICU_CHANGES=1>)
+    $<$<COMPILE_LANGUAGE:C,CXX>:APPLE_ICU_CHANGES=1>
+    $<$<COMPILE_LANGUAGE:C,CXX>:UCHAR_TYPE="char16_t">
+    $<$<COMPILE_LANGUAGE:C,CXX>:U_PLATFORM_IS_DARWIN_BASED=0>)
 
 # Linux specific settings
 if(CMAKE_SYSTEM_NAME STREQUAL Linux)