build: fix link error on MSVC for SFML port

Change two `constexpr` declarations to `inline` to fix a link error on
MSVC.

Also remove the C++14 override that was used for testing on MSVC, the
project being defined as C++17 in CMake.

Signed-off-by: Rafael Kitover <rkitover@gmail.com>

cmake/Toolchain-msvc.cmake

@@ -68,8 +68,6 @@ if(CMAKE_VERSION VERSION_LESS "3.25")
     endif()
 endif()
 
-add_compile_options($<$<COMPILE_LANGUAGE:CXX>:/std:c++14>)
-
 set(CMAKE_RC_FLAGS "-c65001 /DWIN32" CACHE STRING "" FORCE)
 
 # We need to explicitly set all of these to override the CMake defaults.

third_party/sfml/include/SFML/System/Angle.inl

@@ -266,6 +266,10 @@ constexpr Angle operator""_rad(unsigned long long angle)
 
 // Note: the 'inline' keyword here is technically not required, but VS2019 fails
 // to compile with a bogus "multiple definition" error if not explicitly used.
+#ifdef _MSC_VER
+inline constexpr Angle Angle::Zero;
+#else
 constexpr Angle Angle::Zero;
+#endif
 
 } // namespace sf

third_party/sfml/include/SFML/System/Time.inl

@@ -279,6 +279,10 @@ constexpr Time& operator%=(Time& left, Time right)
 
 // Note: the 'inline' keyword here is technically not required, but VS2019 fails
 // to compile with a bogus "multiple definition" error if not explicitly used.
+#ifdef _MSC_VER
+inline constexpr Time Time::Zero;
+#else
 constexpr Time Time::Zero;
+#endif
 
 } // namespace sf