kernel: fix hv tools build for arm64 when cross-built

[Adrian Vladu <avladu@cloudbasesolutions.com>]

Hello,

While trying to build the LIS daemons for Flatcar Container Linux for ARM64 (https://www.flatcar.org/), as we are doing Gentoo based cross-building from X64 boxes, there was an error while building those daemons, because the cross-compile scenario was not working, as ` ARCH := $(shell uname -m 2>/dev/null)` always returns `x86_64`.

I have a working patch for the Linux kernel here that was already applied in the Flatcar context and it works:
https://github.com/flatcar/scripts/blob/94b1df1b19449eb5aa967fd48ba4c1f4a6d5f415/sdk_container/src/third_party/coreos-overlay/sys-kernel/coreos-sources/files/6.10/z0008-tools-hv-fix-cross-compilation-for-ARM64.patch

Raw patch link here: https://raw.githubusercontent.com/flatcar/scripts/94b1df1b19449eb5aa967fd48ba4c1f4a6d5f415/sdk_container/src/third_party/coreos-overlay/sys-kernel/coreos-sources/files/6.10/z0008-tools-hv-fix-cross-compilation-for-ARM64.patch

Sorry for the delivery method via github link, but I cannot send proper patches from my work email address currently, as the email server does not support it.

Please let me know if I need to send the patch via the recommended way or if the patch can be used directly.

Also, maybe there is a better way to address the cross-compilation issue, I just wanted to report the bug and also provide a possible fix.

Thank you,
Adrian Vladu