VS2017/VS2019, with 14.0 toolset: amd64 build fails

It seems this issue is related to the build environment, rather than ReactOS itself (Or is it?).

Guesses:
A "regression", as (VS2015) AppVeyor CI was dropped?
Some VS component is missing on VS2017/VS2019 by default?
A "cross-compile" issue, maybe related to in-progress PR3602?

—

AppVeyor: (restored and updated, and allowing CMake 3.16.2)

• VS2015 itself, on VS2015/VS2017 images:
  Build completes.
• VS2017 as '14.0', on VS2017 image,
  VS2019 as '14.0', on VS2019 image:
  Build fails.

–

GitHub:
Build fails.

10 errors like

[289/12005] Generating dosmbr.bin.obj

FAILED: boot/freeldr/bootsect/dosmbr.bin.obj 

cmd.exe /C "cd /D D:\a\reactos\reactos\build\boot\freeldr\bootsect && "C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\\bin\HostX86\x86\ml.exe" /nologo /Cp /FoD:/a/reactos/reactos/build/boot/freeldr/bootsect/dosmbr.bin.obj /c /Ta D:/a/reactos/reactos/build/boot/freeldr/bootsect/dosmbr.bin.tmp"

The system cannot find the path specified.