You can't.
Windows will rewrite your boot partition, when it feels like it.
It can be commanded to do this remotely, also. Its called a Windows Update. And Windows buries itself below Ring 0 via Pluton/TPMv2.
It does this because the NSA likes being able to keep tabs on everyone.
The precise/exact way this works is hardware/setup dependant, and changes every 6 months or so, ish, but yeah this bootloader fuckery nonsense has been going on for years now, in dual boot setups, and there really is not a plausible explanation for this continuing as a persistent 'problem', other than Windows makes NSA backdoors into your entire system, or breaks shit while trying to.
Dual booting is dumb if you value system security and stability.