esbuild location in /tmp/phx-esbuild causes permission issue on multiuser systems

[nullfractal]

Environment

• Elixir version: 1.12.3
• Phoenix version: 1.6.2
• Operating system: Pop!_OS / Ubuntu

Expected behavior

When setting up/installing a phoenix application on a multi-user system, the path of the /tmp location for esbuild should not cause permission issues if the directory already exists from another user account. This could possibly be addressed by using a user specifc named directory or prefix inside /tmp for the phx-esbuild directory.

Actual behavior

Although this isn't a common scenario I'm guessing (shared computers or computer lab environments would be affected), when one user on a system is developing phoenix apps, esbuild package gets downloaded to /tmp/phx-esbuild and is set for that user's user/group ownership. If another user then logs into the same system and attempts to start or run a phoenix application, the application fails to start because that /tmp/phx-esbuild directory is owned by the other user:

[error] Task #PID<0.534.0> started from MyAppWeb.Endpoint terminating
** (File.Error) could not remove files and directories recursively from "/tmp/phx-esbuild": permission denied

[nullfractal]

@josevalim you are awesome, thanks!