Make 4.3 rebuilds .o files when unnecessary

[Tommaso Fonda]

Hello,
First of all, this is the first time I use a mailing list to seek support -
I hope it's the right place to post my message :)
I often build (a very old version of) the Linux kernel for my Android
smartphone, for reference, my sources are here:
https://github.com/Tomoms/android_kernel_oppo_msm8974
Usually, after changing some source files, only those files are rebuilt
(unless I run "make clean", obviously), and this is what has always
happened until I updated to make 4.3. When using make 4.3, as packaged in
OpenSUSE Tumbleweed and Ubuntu 20.10, running "make" always rebuilds the
whole kernel tree, even when no files have changed since the last time I
completed a build. As soon as I roll back to make 4.2, the behaviour goes
back to normal. Is this a bug?
Thank you for your attention.
Regards,
--
Tommaso Fonda