- fixed platform detection of Apple ARM64 target

cmake/TargetArch.cmake

@@ -96,6 +96,8 @@ function(target_architecture output_var)
                 set(osx_arch_x86_64 TRUE)
             elseif("${osx_arch}" STREQUAL "ppc64" AND ppc_support)
                 set(osx_arch_ppc64 TRUE)
+            elseif("${osx_arch}" STREQUAL "arm64")
+                set(osx_arch_arm64 TRUE)
             else()
                 message(FATAL_ERROR "Invalid OS X arch name: ${osx_arch}")
             endif()
@@ -117,6 +119,10 @@ function(target_architecture output_var)
         if(osx_arch_ppc64)
             list(APPEND ARCH ppc64)
         endif()
+
+        if(osx_arch_arm64)
+            list(APPEND ARCH arm64)
+        endif()
     else()
         file(WRITE "${CMAKE_BINARY_DIR}/arch.c" "${archdetect_c_code}")