Can't build grist from source

I’m trying to build Grist from source on Windows. I’m following these instructions: https://github.com/gristlabs/grist-desktop?tab=readme-ov-file#how-to-build-from-source

I’ve set up msys2 and installed all the dependencies there. Then I got an error about make not being a recognized command, so I installed that as well and started from the beginning again.

The first 3 commands work fine. yarn run setup however crashes with the error

C:\msys64\home\paul.pinterits\grist-desktop\scripts\setup.sh: line 177: cd: core/sandbox/pyodide: No
 such file or directory
error Command failed with exit code 1.

I checked manually and that directory does in fact exist? So I re-ran the command, and that time it completed successfully.

Now I’m stuck at yarn run build. It fails with this error:

+ tsc --build tsconfig-ext.json
ext/desktop.package.json:1:1 - error TS1327: String literal with double quotes expected.

1 ../package.json


ext/desktop.package.json:1:1 - error TS1005: '{' expected.

1 ../package.json
  ~

ext/desktop.package.json:1:1 - error TS1328: Property value can only be string literal, numeric lite
ral, 'true', 'false', 'null', object literal or array literal.

1 ../package.json
  ~~~~~~~~~~~~~~~

ext/desktop.package.json:1:2 - error TS1003: Identifier expected.

1 ../package.json
   ~

ext/desktop.package.json:1:3 - error TS1003: Identifier expected.

1 ../package.json
    ~

ext/desktop.package.json:1:16 - error TS1005: '}' expected.

1 ../package.json



Found 6 errors.

error Command failed with exit code 2.
info Visit https://yarnpkg.com/en/docs/cli/run for documentation about this command.
error Command failed with exit code 2.
info Visit https://yarnpkg.com/en/docs/cli/run for documentation about this command.

It seems that the content of desktop.package.json got messed up somehow. Instead of json, it contains a file path:

$ cat ext/desktop.package.json
../package.json