Make ICU build with Clang. ...

third_party/icu/public/common/unicode/unistr.h

Index: third_party/icu/public/common/unicode/unistr.h
===================================================================
--- third_party/icu/public/common/unicode/unistr.h	(revision 75912)
+++ third_party/icu/public/common/unicode/unistr.h	(working copy)
@@ -4089,7 +4089,7 @@
 #if defined(__GNUC__)
   // Ticket #7039: Clip length to the maximum valid length to the end of addressable memory given the starting address
   // This is only an issue when using GCC and certain optimizations are turned on.
-  return extract(start, _length, dst, dst!=0 ? ((dst >= (char*)((size_t)-1) - UINT32_MAX) ? (((char*)UINT32_MAX) - dst) : UINT32_MAX) : 0, codepage);
+  return extract(start, _length, dst, dst!=0 ? ((dst >= (char*)((size_t)-1) - UINT32_MAX) ? static_cast<unsigned int>((((char*)UINT32_MAX) - dst)) : UINT32_MAX) : 0, codepage);
 #else
   return extract(start, _length, dst, dst!=0 ? 0xffffffff : 0, codepage);
 #endif