Restore the MSVC /utf-8 flag

Author: afarber

CMakeLists.txt

@@ -268,6 +268,7 @@ elseif(CMAKE_CXX_COMPILER_ID MATCHES "MSVC")
   # using Visual Studio C++
   set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} /bigobj") # avoid compiler error C1128 from scripting_environment_lua.cpp
   set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} /DWIN32_LEAN_AND_MEAN") # avoid compiler error C2011 from dual #include of winsock.h and winsock2.h
+  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} /utf-8") # support Unicode in fmt library
   add_dependency_defines(-DBOOST_LIB_DIAGNOSTIC)
   add_dependency_defines(-D_CRT_SECURE_NO_WARNINGS)
   add_dependency_defines(-DNOMINMAX) # avoid min and max macros that can break compilation