Add Python toolcache installation from Github releases for Ubuntu (#704)

Change logic to install Python to Ubuntu images to use GitHub releases from https://github.com/actions/python-versions

images/linux/scripts/installers/Install-Toolset.ps1

@@ -0,0 +1,55 @@
+################################################################################
+##  File:  Install-Toolset.ps1
+##  Team:  CI-Build
+##  Desc:  Install toolset
+################################################################################
+
+Function Install-Asset {
+    param(
+        [Parameter(Mandatory = $true)]
+        [object] $ReleaseAsset
+    )
+
+    Write-Host "Download $($ReleaseAsset.filename)"
+    wget $ReleaseAsset.download_url -nv --retry-connrefused --tries=10
+
+    Write-Host "Extract $($ReleaseAsset.filename) content..."
+    $assetFolderPath = Join-Path $env:INSTALLER_SCRIPT_FOLDER $($ReleaseAsset.filename)
+    New-Item -ItemType Directory -Path $assetFolderPath
+    tar -xzf $ReleaseAsset.filename -C $assetFolderPath
+
+    Write-Host "Invoke installation script..."
+    Push-Location -Path $assetFolderPath
+    Invoke-Expression "bash ./setup.sh"
+    Pop-Location
+}
+
+$ErrorActionPreference = "Stop"
+
+# Get toolset content
+$toolsetJson = Get-Content -Path "$env:INSTALLER_SCRIPT_FOLDER/toolset.json" -Raw
+$tools = ConvertFrom-Json -InputObject $toolsetJson | Select-Object -ExpandProperty toolcache
+
+foreach ($tool in $tools) {
+    # Get versions manifest for current tool
+    $assets = Invoke-RestMethod $tool.url
+
+    # Get github release asset for each version
+    foreach ($toolVersion in $tool.versions) {
+        $asset = $assets | Where-Object version -like $toolVersion `
+        | Select-Object -ExpandProperty files `
+        | Where-Object { ($_.platform -eq $tool.platform) -and ($_.platform_version -eq $tool.platform_version)} `
+        | Select-Object -First 1
+
+        Write-Host "Installing $($tool.name) $toolVersion $($tool.arch)..."
+        if ($asset -ne $null) {
+            Install-Asset -ReleaseAsset $asset
+        }
+        else {
+            Write-Host "Asset was not found in versions manifest"
+            exit 1
+        }
+    }
+}
+
+chown -R "$($env:SUDO_USER):$($env:SUDO_USER)" /opt/hostedtoolcache/Python