PowerShell 6 on Win7 failed to build

Start-Process "" -Wait doesn't wait preventing proper extraction of tools.
See these issues:
* https://github.com/PowerShell/PowerShell/issues/2091  (Main issue)
* https://github.com/PowerShell/PowerShell/issues/3747
* https://github.com/PowerShell/PowerShell/pull/4463

.bin/Scripts/build_kit.ps1

@@ -17,6 +17,15 @@ $host.UI.RawUI.BackgroundColor = "black"
 $host.UI.RawUI.ForegroundColor = "white"
 $progressPreference = 'silentlyContinue'
 
+## Safety Check ##
+if ($PSVersionTable.PSVersion.Major -eq 6 -and $PSVersionTable.OS -imatch "Windows 6.1") {
+    Write-Host -ForegroundColor "Red" "`nAborted."
+    Write-Host "`nThis script doesn't support PowerShell 6.0 on Windows 7."
+	Write-Host "Press Enter to exit... " -NoNewLine
+	Read-Host
+    exit
+}
+
 ## Functions ##
 function download-file {
     param ([String]$path, [String]$name, [String]$url)

README.md

@@ -4,7 +4,7 @@ A collection of scripts to help technicians service Windows systems.
 
 ## Requirements ##
 
-* PowerShell 3.0 or newer
+* PowerShell 3.0 or newer<sup>1</sup>
 * 6 Gb disk space
 
 ## Initial Setup ##
@@ -36,3 +36,6 @@ A collection of scripts to help technicians service Windows systems.
 * `Misc`
 * `Repairs`
 * `Uninstallers`
+
+### Notes ###
+1. PowerShell 6.0 on Windows 7 is not supported by the build script.