Cherry-pick 276049@main (f84f5a2). rdar://102516630

    [generate-xcfilelists] Disable autoinstaller
    https://bugs.webkit.org/show_bug.cgi?id=270921
    rdar://102516630

    Reviewed by Elliott Williams.

    generate-xcfilelists doesn't require the autoinstaller,
    encode that assumption so no dependency is added in the future.

    * Tools/Scripts/generate-xcfilelists:

    Canonical link: https://commits.webkit.org/276049@main

Canonical link: https://commits.webkit.org/272448.728@safari-7618-branch

Tools/Scripts/generate-xcfilelists

@@ -50,8 +50,11 @@
 # does this in order to establish the context in which builds occur. In
 # particular, it does this in order to set needed environment variables.
 
+import os
 import sys
 
+os.environ['DISABLE_WEBKITCOREPY_AUTOINSTALLER'] = '1'
+
 from webkitpy.generate_xcfilelists_lib.application import Application
 from webkitpy.port.config import apple_additions