cmake: kmod: Fix cross compile decision

Consider "arm64" to be "aarch64".
It mistakenly considers cross-compilation when compiled through spack.

Change-Id: I914df482e21517adc1105512ea3d8919ef1577b1

cmake/modules/Kbuild.cmake

@@ -39,7 +39,15 @@ endif(ENABLE_WERROR)
 	else ()
 		set(MAKE "$(MAKE)")
 	endif ()
-	if (NOT "${ARCH}" STREQUAL "${CMAKE_HOST_SYSTEM_PROCESSOR}")
+
+	# Convert McKernel "arm64" into Linux "aarch64"
+	if ("${ARCH}" STREQUAL "arm64")
+		set(LINUX_ARCH "aarch64")
+	else ()
+		set(LINUX_ARCH "${ARCH}")
+	endif ()
+
+	if (NOT "${LINUX_ARCH}" STREQUAL "${CMAKE_HOST_SYSTEM_PROCESSOR}")
 		string(REGEX REPLACE "ld$" "" CROSS_COMPILE "${CMAKE_LINKER}")
 		list(APPEND KBUILD_MAKE_FLAGS "ARCH=${ARCH};CROSS_COMPILE=${CROSS_COMPILE}")
 	endif()