treat armv8 CMAKE_SYSTEM_PROCESSOR as arm64

The cmake scripts incorrectly treated armv8 as 32-bit arm, causing
compilation issues. This just adds 'armv8' to the arm64 condition check.

cmake/system_check.cmake

@@ -54,7 +54,7 @@ elseif(CMAKE_SYSTEM_PROCESSOR MATCHES "amd64.*|x86_64.*|AMD64.*")
   endif()
 elseif(CMAKE_SYSTEM_PROCESSOR MATCHES "i686.*|i386.*|x86.*|amd64.*|AMD64.*")
   set(X86 1)
-elseif(CMAKE_SYSTEM_PROCESSOR MATCHES "^(aarch64.*|AARCH64.*|arm64.*|ARM64.*)")
+elseif(CMAKE_SYSTEM_PROCESSOR MATCHES "^(aarch64.*|AARCH64.*|arm64.*|ARM64.*|armv8.*)")
   if("${CMAKE_SIZEOF_VOID_P}" EQUAL "8")
     set(ARM64 1)
   else()