Use npm to install pnpm

CommandMC · CommandMC · commit 999493e25d18 · 2024-04-08T15:06:02.000+02:00
Corepack installs the non-standalone version, which of course doesn't work with
electron-builder
diff --git a/appveyor.yml b/appveyor.yml
@@ -8,8 +8,7 @@ init:
 
 install:
   - pip install castlabs-evs
-  - corepack enable
-  - corepack prepare pnpm@latest-8 --activate
+  - npm install -g @pnpm/exe
   - pnpm install
 
 environment:
