Yeah, it picks it up. But I mean in the readme, you can mention that widl can be obtained from something besides Wine (it says there you need Wine).

mingw-w64-tools is a lot smaller than wine64-tools.

Hm, I tried to build the dll and it complained that widl wasn't found and failed. Let me try again without widl.

Yep:

meson --cross-file build-win64.txt -Denable_standalone_d3d12=True --buildtype release --prefix $HOME/mnt/vmshare/vkd3d-64 build.64
The Meson build system
Version: 0.55.3
Source dir: /home/user/build/vkd3d-proton
Build dir: /home/user/build/vkd3d-proton/build.64
Build type: cross build
Project name: vkd3d
Project version: 1.1
C compiler for the build machine: cc (gcc 10.2.0 "cc (Debian 10.2.0-15) 10.2.0")
C linker for the build machine: cc ld.bfd 2.35.1
C compiler for the host machine: x86_64-w64-mingw32-gcc (gcc 10.0.0 "x86_64-w64-mingw32-gcc (GCC) 10-posix 20200525")
C linker for the host machine: x86_64-w64-mingw32-gcc ld.bfd 2.35
Build machine cpu family: x86_64
Build machine cpu: x86_64
Host machine cpu family: x86_64
Host machine cpu: x86_64
Target machine cpu family: x86_64
Target machine cpu: x86_64
Program widl found: NO

meson.build:50:0: ERROR: Program 'widl' not found

Oh. You mean widl is always needed, but for .dll it uses mingw widl, and for .so it needs wine widl?

Then you can mention that widl is needed from mingw tools in case of dll, just to be clear. Because apparently on Debian it requires an extra package.

May be it is a bit implicit, but the readme already says so:
Mingw-w64 compiler, headers and tools (at least version 7.0) [for cross-builds for d3d12.dll which are default]

I guess, but since widl already is featured for .so explicitly, it would make it a bit more clear to mention it for .dll build too.

At least I had no idea it was needed until the build failure :)