VDSOEmulation: Support loading VDSO thunk as shared

Just requires a thread pointer check to be fixed in FEXCore.
This doesn't need unique pages to exist for the file mapping and can be
shared since it's readonly mapped.

FEXCore/Source/Interface/Core/Core.cpp

@@ -950,6 +950,8 @@ void ContextImpl::InvalidateGuestCodeRange(FEXCore::Core::InternalThreadState* T
 }
 
 void ContextImpl::MarkMemoryShared(FEXCore::Core::InternalThreadState* Thread) {
+  if (!Thread) return;
+
   if (!IsMemoryShared) {
     IsMemoryShared = true;
     UpdateAtomicTSOEmulationConfig();

Source/Tools/LinuxEmulation/VDSO_Emulation.cpp

@@ -746,7 +746,7 @@ VDSOMapping LoadVDSOThunks(bool Is64Bit, FEX::HLE::SyscallHandler* const Handler
       Mapping.VDSOSize = FEXCore::AlignUp(Mapping.VDSOSize, 4096);
 
       // Map the VDSO file to memory
-      Mapping.VDSOBase = Handler->GuestMmap(nullptr, nullptr, Mapping.VDSOSize, PROT_READ, MAP_PRIVATE, VDSOFD, 0);
+      Mapping.VDSOBase = Handler->GuestMmap(nullptr, nullptr, Mapping.VDSOSize, PROT_READ, MAP_SHARED, VDSOFD, 0);
 
       // Since we found our VDSO thunk library, find our host VDSO function implementations.
       LoadHostVDSO();