Can't package on linux 4.21(worked on 4.20)

I get the output below when trying to package for linux on 4.21.

This worked on 4.20.

I’m using a newer version of toolchain v12_clang-6.0.1-centos7.

Full package log can be found here:

PackagingResults: Warning: URL: ../../../Engine/Binaries/Win64/CrashReportClient.exe "D:/UnrealProjects/mygame/Saved/Crashes/UE4CC-Windows-83473F8344DF28DD393015823B642E12_0000" -Unattended -nullrhi -AppName=UE4-MyGame -CrashGUID=UE4CC-Windows-83473F8344DF28DD393015823B642E12_0000 -DebugSymbols=..\..\..\Engine\Intermediate\Symbols
PackagingResults: Error: begin: stack for UAT
PackagingResults: Error: === Critical error: ===
PackagingResults: Error: Assertion failed: CurrentJob.bSucceeded [File:C:\UnrealEngine-4.21.0-release\Engine\Source\Runtime\Engine\Private\Materials\MeshMaterialShader.cpp] [Line: 122]
PackagingResults: Error: [Callstack] 0x00007ffaacc3a388 KERNELBASE.dll!UnknownFunction []
PackagingResults: Error: [Callstack] 0x00007ffa81279b5a UE4Editor-Core.dll!FWindowsErrorOutputDevice::Serialize() [c:\unrealengine-4.21.0-release\engine\source\runtime\core\private\windows\windowserroroutputdevice.cpp:63]
PackagingResults: Error: [Callstack] 0x00007ffa810273e7 UE4Editor-Core.dll!FOutputDevice::LogfImpl() [c:\unrealengine-4.21.0-release\engine\source\runtime\core\private\misc\outputdevice.cpp:71]
PackagingResults: Error: [Callstack] 0x00007ffa80fac5b7 UE4Editor-Core.dll!FDebug::AssertFailed() [c:\unrealengine-4.21.0-release\engine\source\runtime\core\private\misc\assertionmacros.cpp:417]
PackagingResults: Error: [Callstack] 0x00007ffa570bd12f UE4Editor-Engine.dll!FMeshMaterialShaderType::FinishCompileShader() [c:\unrealengine-4.21.0-release\engine\source\runtime\engine\private\materials\meshmaterialshader.cpp:123]
PackagingResults: Error: [Callstack] 0x00007ffa57055fc6 UE4Editor-Engine.dll!FMaterialShaderMap::ProcessCompilationResultsForSingleJob() [c:\unrealengine-4.21.0-release\engine\source\runtime\engine\private\materials\materialshader.cpp:1638]
PackagingResults: Error: [Callstack] 0x00007ffa570537a7 UE4Editor-Engine.dll!FMaterialShaderMap::ProcessCompilationResults() [c:\unrealengine-4.21.0-release\engine\source\runtime\engine\private\materials\materialshader.cpp:1695]
PackagingResults: Error: [Callstack] 0x00007ffa574680e0 UE4Editor-Engine.dll!FShaderCompilingManager::ProcessCompiledShaderMaps() [c:\unrealengine-4.21.0-release\engine\source\runtime\engine\private\shadercompiler\shadercompiler.cpp:1960]
PackagingResults: Error: [Callstack] 0x00007ffa5744d097 UE4Editor-Engine.dll!FShaderCompilingManager::FinishCompilation() [c:\unrealengine-4.21.0-release\engine\source\runtime\engine\private\shadercompiler\shadercompiler.cpp:2465]
PackagingResults: Error: [Callstack] 0x00007ffa5702d4bd UE4Editor-Engine.dll!FMaterial::FinishCompilation() [c:\unrealengine-4.21.0-release\engine\source\runtime\engine\private\materials\materialshared.cpp:543]
PackagingResults: Error: [Callstack] 0x00007ffa5706d4b7 UE4Editor-Engine.dll!FMaterial::SerializeInlineShaderMap() [c:\unrealengine-4.21.0-release\engine\source\runtime\engine\private\materials\materialshared.cpp:833]
PackagingResults: Error: [Callstack] 0x00007ffa56fbf719 UE4Editor-Engine.dll!SerializeInlineShaderMaps() [c:\unrealengine-4.21.0-release\engine\source\runtime\engine\private\materials\material.cpp:663]
PackagingResults: Error: [Callstack] 0x00007ffa56fbc3e3 UE4Editor-Engine.dll!UMaterial::Serialize() [c:\unrealengine-4.21.0-release\engine\source\runtime\engine\private\materials\material.cpp:3441]
PackagingResults: Error: [Callstack] 0x00007ffa6af7da3b UE4Editor-CoreUObject.dll!FArchiveSaveTagExports::ProcessTaggedObjects() [c:\unrealengine-4.21.0-release\engine\source\runtime\coreuobject\private\uobject\savepackage.cpp:1155]
PackagingResults: Error: [Callstack] 0x00007ffa6afa29a7 UE4Editor-CoreUObject.dll!FPackageExportTagger::TagPackageExports() [c:\unrealengine-4.21.0-release\engine\source\runtime\coreuobject\private\uobject\savepackage.cpp:2886]
PackagingResults: Error: [Callstack] 0x00007ffa6af878cb UE4Editor-CoreUObject.dll!UPackage::Save() [c:\unrealengine-4.21.0-release\engine\source\runtime\coreuobject\private\uobject\savepackage.cpp:3776]
PackagingResults: Error: [Callstack] 0x00007ffa55060247 UE4Editor-UnrealEd.dll!UEditorEngine::Save() [c:\unrealengine-4.21.0-release\engine\source\editor\unrealed\private\editorengine.cpp:4441]
PackagingResults: Error: [Callstack] 0x00007ffa54f02b9b UE4Editor-UnrealEd.dll!UCookOnTheFlyServer::SaveCookedPackage() [c:\unrealengine-4.21.0-release\engine\source\editor\unrealed\private\cookontheflyserver.cpp:3988]
PackagingResults: Error: [Callstack] 0x00007ffa54f053c1 UE4Editor-UnrealEd.dll!UCookOnTheFlyServer::SaveCookedPackages() [c:\unrealengine-4.21.0-release\engine\source\editor\unrealed\private\cookontheflyserver.cpp:2896]
PackagingResults: Error: [Callstack] 0x00007ffa54f10672 UE4Editor-UnrealEd.dll!UCookOnTheFlyServer::TickCookOnTheSide() [c:\unrealengine-4.21.0-release\engine\source\editor\unrealed\private\cookontheflyserver.cpp:2372]
PackagingResults: Error: [Callstack] 0x00007ffa54d73e7b UE4Editor-UnrealEd.dll!UCookCommandlet::CookByTheBook() [c:\unrealengine-4.21.0-release\engine\source\editor\unrealed\private\commandlets\cookcommandlet.cpp:882]
PackagingResults: Error: [Callstack] 0x00007ffa54da5f3f UE4Editor-UnrealEd.dll!UCookCommandlet::Main() [c:\unrealengine-4.21.0-release\engine\source\editor\unrealed\private\commandlets\cookcommandlet.cpp:586]
PackagingResults: Error: [Callstack] 0x00007ff7cee3df15 UE4Editor-Cmd.exe!FEngineLoop::PreInit() [c:\unrealengine-4.21.0-release\engine\source\runtime\launch\private\launchengineloop.cpp:2478]
PackagingResults: Error: [Callstack] 0x00007ff7cee34ae2 UE4Editor-Cmd.exe!GuardedMain() [c:\unrealengine-4.21.0-release\engine\source\runtime\launch\private\launch.cpp:135]
PackagingResults: Error: [Callstack] 0x00007ff7cee34d2a UE4Editor-Cmd.exe!GuardedMainWrapper() [c:\unrealengine-4.21.0-release\engine\source\runtime\launch\private\windows\launchwindows.cpp:145]
PackagingResults: Error: [Callstack] 0x00007ff7cee43aaa UE4Editor-Cmd.exe!WinMain() [c:\unrealengine-4.21.0-release\engine\source\runtime\launch\private\windows\launchwindows.cpp:276]
PackagingResults: Error: [Callstack] 0x00007ff7cee44a16 UE4Editor-Cmd.exe!__scrt_common_main_seh() [f:\dd\vctools\crt\vcstartup\src\startup\exe_common.inl:288]
PackagingResults: Error: [Callstack] 0x00007ffaad583034 KERNEL32.DLL!UnknownFunction []
PackagingResults: Error: [Callstack] 0x00007ffaafca1461 ntdll.dll!UnknownFunction []

This was fixed in 4.21.1. If you don’t want to sync all the engine, you can integrate just this change: https://github.com/EpicGames/UnrealEngine/commit/ffad25a8090718d316f8bedc5aa0c97e9c03c198