[JITLink] Always unmap standard segments in InProcessMemoryManager::d…

…eallocate (#81943)

Right now InProcessMemoryManager only releases a standard segment (via
sys::Memory::releaseMappedMemory) in `deallocate` when there is a
DeallocAction associated, leaving residual memory pages in the process
until termination.
Despite being a de facto memory leak, it won't cause a major issue if
users only create a single LLJIT instance per process, which is the most
common use cases. It will, however, drain virtual memory pages if we
create thousands of ephemeral LLJIT instances in the same process.

This patch fixes this issue by releasing every standard segments
regardless of the attached DeallocAction.

llvm/lib/ExecutionEngine/JITLink/JITLinkMemoryManager.cpp

@@ -449,8 +449,7 @@ void InProcessMemoryManager::deallocate(std::vector<FinalizedAlloc> Allocs,
     for (auto &Alloc : Allocs) {
       auto *FA = Alloc.release().toPtr<FinalizedAllocInfo *>();
       StandardSegmentsList.push_back(std::move(FA->StandardSegments));
-      if (!FA->DeallocActions.empty())
-        DeallocActionsList.push_back(std::move(FA->DeallocActions));
+      DeallocActionsList.push_back(std::move(FA->DeallocActions));
       FA->~FinalizedAllocInfo();
       FinalizedAllocInfos.Deallocate(FA);
     }