Linux: Writing a Windows MBR instead of grub

On a test computer, I use /dev/sda1 to contain whatever operating system I need for the moment. At some point, I installed Linux Mint 19.1 properly on that partition, and then I wanted to return to Windows 10. After writing the Windows 10 image to /dev/sda1, I got a message from grub saying it didn’t detect the filesystem.

Hmmm… So the MBR was overwritten by GRUB, and now I need to get it back to Windowish. One can use Microsoft’s rescue disk-on-key, or the quick hack: Download ms-sys, compile with plain “make”, don’t bother to install, and just go from the bin/ directory:

# ./ms-sys -7 /dev/sda

and Windows 10 boots like a charm.