A different approach to my changes in https://github.com/MinecraftForge/MinecraftForge/commit/8ace535995522bec0557d4217e0d98b3dc76cf1e to fix #5207

build.gradle

@@ -88,6 +88,7 @@ license {
     header = project.file('LICENSE-header.txt')
 
     include 'net/minecraftforge/'
+    exclude 'net/minecraftforge/api/distmarker/'
     exclude 'net/minecraftforge/fml/repackage/'
     exclude 'net/minecraftforge/server/terminalconsole/'
     exclude 'net/minecraftforge/fml/common/versioning/ComparableVersion.java'

src/main/java/net/minecraftforge/fml/common/launcher/FMLTweaker.java

@@ -122,6 +122,8 @@ public class FMLTweaker implements ITweaker {
 
         Yggdrasil.login(launchArgs);
 
+        Launch.blackboard.put("forgeLaunchArgs", Maps.newHashMap(launchArgs));
+
         try
         {
             jarLocation = getClass().getProtectionDomain().getCodeSource().getLocation().toURI();
@@ -143,6 +145,11 @@ public class FMLTweaker implements ITweaker {
     @Override
     public String getLaunchTarget()
     {
+        // Remove the extraneous mods and modListFile args
+        @SuppressWarnings("unchecked")
+        Map<String,String> args = (Map<String, String>) Launch.blackboard.get("launchArgs");
+        args.remove("--modListFile");
+        args.remove("--mods");
         return "net.minecraft.client.main.Main";
     }
 
@@ -154,11 +161,10 @@ public class FMLTweaker implements ITweaker {
 
         for (Entry<String, String> arg : launchArgs.entrySet())
         {
-            if ("--modListFile".equals(arg.getKey()) || "--mods".equals(arg.getKey()))
-                continue;
             args.add(arg.getKey());
             args.add(arg.getValue());
         }
+        launchArgs.clear();
 
         return args.toArray(new String[args.size()]);
     }

src/main/java/net/minecraftforge/fml/relauncher/libraries/LibraryManager.java

@@ -443,7 +443,7 @@ public class LibraryManager
         List<File> list = new ArrayList<>();
 
         @SuppressWarnings("unchecked")
-        Map<String,String> args = (Map<String, String>)Launch.blackboard.get("launchArgs");
+        Map<String,String> args = (Map<String, String>)Launch.blackboard.get("forgeLaunchArgs");
         String extraMods = args.get("--mods");
         if (extraMods != null)
         {