Hm, the makefile doesn't seem to do anything special. Looks to me like you should bring up this issue with the emscripten developers.
I use WSL for emscripten development by the way because the whole emscripten toolchain seems to be more at home on Linux.

Looks like an emscripten setup issue, it can't seem to find your python.exe. Can you compile regular emscripten projects?

PS: And as you're saying python is at that path - maybe it needs to use a cygwin style path (/cygdrive/d/...). But anyway, get regular emscripten projects going first.

Hmm, yes, that's definitely important. Please open a GitHub issue, will try to get that in soon.

Ah, that tells us what's going on. Electron (which is used to run html5-debug builds) can not enable WebGL on your system (might be a black-listed driver or whatever) and then loading shaders of course fails.

But that works fine for me. Can you show me the complete build output?

But but... that makes no sense. What exactly do you mean by compiling in debug mode?

Kha and its submodules are not in sync (that's what the first line in the build output tries to tell you). Have a look at the "Updating Kha" paragraph at https://github.com/Kode/Kha/wiki/Getting-Started

Initial build output from Kha/make or vscode too please.

Looks like the stride is not calculated correctly. Please open an issue on GitHub.

Can not reproduce that, please show us your complete build output.