Revert to once again use the legacy build system

New build system seems to cause issues when some targets
are built in parallel. More research is needed as to why.

PiperOrigin-RevId: 217316372
diff --git a/src/TulsiGenerator/XcodeProjectGenerator.swift b/src/TulsiGenerator/XcodeProjectGenerator.swift
index b12ab82..4cd9dac 100644
--- a/src/TulsiGenerator/XcodeProjectGenerator.swift
+++ b/src/TulsiGenerator/XcodeProjectGenerator.swift
@@ -559,6 +559,7 @@
 
     let workspaceSharedDataURL = projectURL.appendingPathComponent("project.xcworkspace/xcshareddata")
     let sharedWorkspaceSettings: [String: Any] = [
+      "BuildSystemType": "Original",
       "IDEWorkspaceSharedSettings_AutocreateContextsIfNeeded": false as AnyObject,
     ]
     try writeWorkspaceSettings(sharedWorkspaceSettings,