cmake: Use C++latest everywhere on MSVC.

CMakeLists.txt

@@ -25,6 +25,14 @@ endif()
 
 project(dolphin-emu)
 
+if (MSVC)
+  set(CMAKE_C_STANDARD 99)
+  set(CMAKE_CXX_STANDARD 20)
+  set(CMAKE_CXX20_STANDARD_COMPILE_OPTION "-std:c++latest")
+  set(CMAKE_CXX_STANDARD_REQUIRED ON)
+  set(CMAKE_CXX_EXTENSIONS OFF)
+endif()
+
 # Name of the Dolphin distributor. If you redistribute Dolphin builds (forks,
 # unofficial builds) please consider identifying your distribution with a
 # unique name here.

Externals/FreeSurround/CMakeLists.txt

@@ -1,6 +1,8 @@
+if (NOT MSVC)
   set(CMAKE_CXX_STANDARD 14)
   set(CMAKE_CXX_STANDARD_REQUIRED ON)
   set(CMAKE_CXX_EXTENSIONS OFF)
+endif()
 
 set(SRCS
   source/ChannelMaps.cpp

Externals/WIL/tests/cpplatest/CMakeLists.txt

@@ -1,7 +1,9 @@
 
 # Compilers often don't use the latest C++ standard as the default. Periodically update this value (possibly conditioned
 # on compiler) as new standards are ratified/support is available
+if (NOT MSVC)
   set(CMAKE_CXX_STANDARD 17)
+endif()
 
 project(witest.cpplatest)
 add_executable(witest.cpplatest)

Externals/cubeb/CMakeLists.txt

@@ -15,9 +15,12 @@ endif()
 if(POLICY CMP0063)
   cmake_policy(SET CMP0063 NEW)
 endif()
+
+if (NOT MSVC)
   set(CMAKE_C_STANDARD 99)
   set(CMAKE_CXX_STANDARD 11)
   set(CMAKE_CXX_STANDARD_REQUIRED ON)
+endif()
 
 if(NOT COMMAND add_sanitizers)
   list(APPEND CMAKE_MODULE_PATH "${PROJECT_SOURCE_DIR}/cmake/sanitizers-cmake/cmake")

Externals/discord-rpc/src/CMakeLists.txt

@@ -4,7 +4,9 @@ option(ENABLE_IO_THREAD "Start up a separate I/O thread, otherwise I'd need to c
 option(USE_STATIC_CRT "Use /MT[d] for dynamic library" OFF)
 option(WARNINGS_AS_ERRORS "When enabled, compiles with `-Werror` (on *nix platforms)." OFF)
 
+if (NOT MSVC)
   set(CMAKE_CXX_STANDARD 14)
+endif()
 
 set(BASE_RPC_SRC
     ${PROJECT_SOURCE_DIR}/include/discord_rpc.h

Externals/imgui/CMakeLists.txt

@@ -1,6 +1,8 @@
+if (NOT MSVC)
   set(CMAKE_CXX_STANDARD 17)
   set(CMAKE_CXX_STANDARD_REQUIRED ON)
   set(CMAKE_CXX_EXTENSIONS OFF)
+endif()
 
 set(SRCS
   imgui.cpp

Source/CMakeLists.txt

@@ -18,15 +18,12 @@ if(CMAKE_SYSTEM_NAME MATCHES "Windows")
   add_definitions(-D_SILENCE_CXX20_OLD_SHARED_PTR_ATOMIC_SUPPORT_DEPRECATION_WARNING)
 endif()
 
-if (MSVC)
+if (NOT MSVC)
-  set(CMAKE_CXX_STANDARD 20)
-  set(CMAKE_CXX20_STANDARD_COMPILE_OPTION "-std:c++latest")
-else()
   set(CMAKE_CXX_STANDARD 17)
-endif()
-
   set(CMAKE_CXX_STANDARD_REQUIRED ON)
   set(CMAKE_CXX_EXTENSIONS OFF)
+endif()
+
 set(CMAKE_EXPORT_COMPILE_COMMANDS ON)
 
 if (MSVC)