CMakeLists: Add architecture detection for AArch64

We already have an equivalent in place for the 32-bit ARM architecture, so we
should also have one for the newer 64-bit ARM architecture as well.

CMakeLists.txt

@@ -66,10 +66,12 @@ if (NOT ENABLE_GENERIC)
         detect_architecture("_M_AMD64" x86_64)
         detect_architecture("_M_IX86" x86)
         detect_architecture("_M_ARM" ARM)
+        detect_architecture("_M_ARM64" ARM64)
     else()
         detect_architecture("__x86_64__" x86_64)
         detect_architecture("__i386__" x86)
         detect_architecture("__arm__" ARM)
+        detect_architecture("__aarch64__" ARM64)
     endif()
 endif()