ARM64: Enable shorten-64-to-32 warning

src/arm64/utils-arm64.cc

Index: src/arm64/utils-arm64.cc
diff --git a/src/arm64/utils-arm64.cc b/src/arm64/utils-arm64.cc
index dbfb87638bccbf88ec81b22d1c653ccd2c8e4e9c..aff191874d99beb5981ff21c78d2a2262dcd5416 100644
--- a/src/arm64/utils-arm64.cc
+++ b/src/arm64/utils-arm64.cc
@@ -74,7 +74,7 @@ int CountSetBits(uint64_t value, int width) {
   value = ((value >> 16) & 0x0000ffff0000ffff) + (value & 0x0000ffff0000ffff);
   value = ((value >> 32) & 0x00000000ffffffff) + (value & 0x00000000ffffffff);
 
-  return value;
+  return static_cast<int>(value);
 }