Updating pre-build pnpm binary

[ltdu]

Some of us use pre-build pnpm binaries. Once new version becomes available, we all receive notification about it. However, default update path pnpm add -g pnpm is not correct for us. We have to execute standalone installation script or download updated executable manually.

We should improve this.

• For starters, I think we should remove pnpm add -g pnpm part from "Update available!" message if pnpm is pre-built. This could help to avoid some issues
• We could replace that command with something like pnpm --package @pnpm/linux-x64 dlx pnpm setup or pnpm --package @pnpm/win-x64 dlx pnpm setup (depending on platform)
  • This does not work currently, because you cannot replace executable while it is still running. And the command is a little too long.
• Introduce new sub-command for pnpm setup. Maybe something like pnpm setup update.

Thoughts?