Update CMake to handle ARM64EC with VS Generator (#199)

Author: walbourn

CMakeLists.txt

@@ -93,6 +93,8 @@ elseif(CMAKE_GENERATOR_PLATFORM MATCHES "^[Aa][Rr][Mm]$")
     set(DXMATH_ARCHITECTURE arm)
 elseif(CMAKE_GENERATOR_PLATFORM MATCHES "^[Aa][Rr][Mm]64$")
     set(DXMATH_ARCHITECTURE arm64)
+elseif(CMAKE_GENERATOR_PLATFORM MATCHES "^[Aa][Rr][Mm]64EC$")
+    set(DXMATH_ARCHITECTURE arm64ec)
 elseif(CMAKE_VS_PLATFORM_NAME_DEFAULT MATCHES "^[Ww][Ii][Nn]32$")
     set(DXMATH_ARCHITECTURE x86)
 elseif(CMAKE_VS_PLATFORM_NAME_DEFAULT MATCHES "^[Xx]64$")
@@ -101,6 +103,8 @@ elseif(CMAKE_VS_PLATFORM_NAME_DEFAULT MATCHES "^[Aa][Rr][Mm]$")
     set(DXMATH_ARCHITECTURE arm)
 elseif(CMAKE_VS_PLATFORM_NAME_DEFAULT MATCHES "^[Aa][Rr][Mm]64$")
     set(DXMATH_ARCHITECTURE arm64)
+elseif(CMAKE_VS_PLATFORM_NAME_DEFAULT MATCHES "^[Aa][Rr][Mm]64EC$")
+    set(DXMATH_ARCHITECTURE arm64ec)
 elseif(NOT (DEFINED DXMATH_ARCHITECTURE))
     set(DXMATH_ARCHITECTURE "x64")
 endif()