Allow vcpkg to be built arm64ec. (#1319)

We have no reason to build vcpkg as arm64ec, but the C++ compiler team have asked us to make this work since they use us as a test case.

Unfortunately, CMake's defaults ( https://gitlab.kitware.com/cmake/cmake/-/blob/master/Modules/Platform/Windows-MSVC.cmake#L243 ) take the pretty names AMD64 and ARM64EC which we use in the COFF file reader. This removes those defines.

CMakeLists.txt

@@ -104,6 +104,12 @@ if(MSVC)
         string(APPEND CMAKE_EXE_LINKER_FLAGS_RELEASE " /CETCOMPAT")
     endif()
 
+    # Avoid CMake's default taking of the pretty names
+    string(REPLACE "/DAMD64" "" CMAKE_C_FLAGS "${CMAKE_C_FLAGS}")
+    string(REPLACE "/DAMD64" "" CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}")
+    string(REPLACE "/DARM64EC" "" CMAKE_C_FLAGS "${CMAKE_C_FLAGS}")
+    string(REPLACE "/DARM64EC" "" CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}")
+
     if(VCPKG_DEVELOPMENT_WARNINGS)
         string(APPEND CMAKE_C_FLAGS " /W4 /sdl")
         string(APPEND CMAKE_CXX_FLAGS " /W4 /sdl")