Switch packages for Ubuntu & macOS to use tar.gz format instead of zip (#6)

Switch to using tar.gz format for Ubuntu and macOS systems because it is much more common on nix systems which is important in container scenarios

helpers/nix-helpers.psm1

@@ -12,5 +12,21 @@ function Extract-TarArchive {
 
     Write-Debug "Extract $ArchivePath to $OutputDirectory"
     tar -C $OutputDirectory -xzf $ArchivePath --strip 1
+}
 
+function Create-TarArchive {
+    param(
+        [Parameter(Mandatory=$true)]
+        [String]$SourceFolder,
+        [Parameter(Mandatory=$true)]
+        [String]$ArchivePath,
+        [string]$CompressionType = "gz"
+    )
+
+    $CompressionTypeArgument = If ([string]::IsNullOrWhiteSpace($CompressionType)) { "" } else { "--${CompressionType}" }
+
+    Push-Location $SourceFolder
+    Write-Debug "tar -c $CompressionTypeArgument -f $ArchivePath ."
+    tar -c $CompressionTypeArgument -f $ArchivePath .
+    Pop-Location
 }