Inno setup pascal script call power shell script file by relative path doesn't work

Question

In test.ps1: Remove-Item -Path  "E:\temp\123.txt" -Force -ErrorAction Continue

In example.iss:

#define path "..\functions\test.ps1"
;#define path "E:\source\functions\test.ps1"

[Code]
var 
    ResultCode : Integer;
function PrepareToInstall(var NeedsRestart: Boolean): String;
    begin
        Exec('cmd', '/C powershell.exe -ExecutionPolicy bypass -File "{#path}"', '', SW_SHOW, 
                ewWaitUntilTerminated, ResultCode);
    end

The example.iss file is in E:\source\installer. The powershell task is simple, which works fine in command line with both full path and the relative path. However in Inno setup, only the full path works (123.txt gets removed). It didn't work with the relative path.

I tried to place test.ps1 in the current folder with .\test.ps1, it didn't work either. The output folder(where the install exe was) was also tried, no luck as well.

Why it only works with the full path E:\source\functions\test.ps1?