Set source character sets to UTF-8

This suppress warning C4819.
https://docs.microsoft.com/en-us/cpp/build/reference/utf-8-set-source-and-executable-character-sets-to-utf-8?view=msvc-160

cmake/Modules/MacroQbtCommonConfig.cmake

@@ -70,8 +70,12 @@ macro(qbt_common_config)
  endif()
 
  if (MSVC)
- target_compile_options(qbt_common_cfg INTERFACE /guard:cf)
- target_link_options(qbt_common_cfg INTERFACE /guard:cf
+ target_compile_options(qbt_common_cfg INTERFACE
+ /guard:cf
+ /utf-8
+ )
+ target_link_options(qbt_common_cfg INTERFACE
+ /guard:cf
  $<$<NOT:$<CONFIG:Debug>>:/OPT:REF /OPT:ICF>
  # suppress linking warning due to /INCREMENTAL and /OPT:ICF being both ON
  $<$<CONFIG:RelWithDebInfo>:/INCREMENTAL:NO>

src/base/unicodestrings.h

@@ -1,4 +1,4 @@
-/*
+/*
  * Bittorrent Client using Qt and libtorrent.
  * Copyright (C) 2015 Mike Tzou
  *
@@ -28,11 +28,6 @@
 
 #pragma once
 
-// This file must be encoded in "UTF-8 with BOM"
-#ifdef _MSC_VER
-#pragma execution_character_set("utf-8")
-#endif
-
 // Because of the poor handling of UTF-8 characters in MSVC (emits warning C4819),
 // we put all problematic UTF-8 chars/strings in this file.
 // See issue #3059 for more details (https://github.com/qbittorrent/qBittorrent/issues/3059).

winconf.pri

@@ -40,7 +40,7 @@ win32-g++* {
 }
 else:win32-msvc* {
  CONFIG -= embed_manifest_exe
- QMAKE_CXXFLAGS += /std:c++17
+ QMAKE_CXXFLAGS += /std:c++17 /utf-8
  QMAKE_LFLAGS += "/MANIFEST:EMBED /MANIFESTINPUT:$$quote($${PWD}/src/qbittorrent.exe.manifest) /STACK:0x800000"
 
  RC_FILE = qbittorrent.rc