fix: count files shared by systems apart

The systems step and --list-systems gave 3do 1704 files, 349 MB, of
which 1689 are MAME hash and plugin files six systems carry. Each line
now shows the system's own files, and the shared ones beside them.

install.ps1

@@ -11,7 +11,7 @@
 
     $ErrorActionPreference = "Stop"
     $defaultInstallUrl = "https://raw.githubusercontent.com/Abdess/retrobios/main/install.py"
-    $defaultInstallSha256 = "739a28ac23d5b0d82d8324ecd7665b2501c71c64d60abba175575f7f16f24ddc"
+    $defaultInstallSha256 = "441fc1f7887aff7808b7b41182fdb18868ce36a50a2bbbba9bb81e595cb3b732"
     $maximumInstallerBytes = 2MB
     $installerExit = 0
     $installer = if ($PSScriptRoot) { Join-Path $PSScriptRoot "install.py" } else { $null }