Update CMake to detect the Apple M1 correctly

On  Apple M1 machines, building failed to determine the system was an arm machine and therefore failed to build with the appropriate intrinsic header.
Adding a check for `arm64` fixes the issue.

cmake/CheckCXXIntrinsicsHeader.cmake

@@ -9,7 +9,7 @@ if(SEAL_USE_INTRIN)
     if(MSVC)
         set(SEAL_INTRIN_HEADER "intrin.h")
     else()
-        if(CMAKE_SYSTEM_PROCESSOR STREQUAL "aarch64")
+        if(CMAKE_SYSTEM_PROCESSOR STREQUAL "aarch64" OR CMAKE_SYSTEM_PROCESSOR STREQUAL "arm64")
             set(SEAL_ARM64 ON)
         else()
             set(SEAL_ARM64 OFF)