Remove hardcoded download path

Previously all files got downloaded to a hardcoded path, including the
username for the CI machines. Usually, it does not fit the username of a
local development machine, complicating to reproduce bugs.

Introduce Get-(Default)DownloadLocation functions in helpers to
specify the default download location. This helps to run the
provisioning scripts on a local machine.

Change-Id: I761a92bf5e3e774358756a95dddb9a5d6ee54db9
Reviewed-by: Oliver Wolff <oliver.wolff@qt.io>

coin/provisioning/common/windows/helpers.ps1

@@ -68,6 +68,17 @@ function BadParam
     throw("You must specify $Description")
 }
 
+function Get-DefaultDownloadLocation
+{
+    return $env:USERPROFILE + "\downloads\"
+}
+
+function Get-DownloadLocation
+{
+    Param ([string]$TargetName = $(BadParam("a target filename")))
+    return (Get-DefaultDownloadLocation) + $TargetName
+}
+
 function Download
 {
     Param (