vagrant environment: install msys2 from our own package source

Author: rgl

Vagrantfile-provision.ps1

@@ -87,7 +87,17 @@ git config --global mergetool.meld.cmd '\"C:/Program Files (x86)/Meld/Meld.exe\"
 #git config --list --show-origin
 
 # install msys2.
-choco install -y msys2
+# NB we have to manually build the msys2 package from source because the
+#    current chocolatey package is somewhat brittle to install.
+Push-Location $env:TEMP
+$p = Start-Process git clone,https://github.com/rgl/choco-packages -PassThru -Wait
+if ($p.ExitCode) {
+    throw "git failed with exit code $($p.ExitCode)"
+}
+cd choco-packages/msys2
+choco pack
+choco install -y msys2 -Source $PWD
+Pop-Location
 
 # configure the msys2 launcher to let the shell inherith the PATH.
 $msys2BasePath = 'C:\tools\msys64'