UserspaceEmulator: Mark mmap regions as malloc blocks when mallocing

We don't have to be clever at all to figure out which MmapRegions are
malloc blocks, we can just mark the containing region as such when
the emulated process performs a malloc! :^)

DevTools/UserspaceEmulator/MallocTracer.cpp

@@ -44,6 +44,10 @@ void MallocTracer::target_did_malloc(Badge<SoftCPU>, FlatPtr address, size_t siz
     ASSERT(region);
     ASSERT(region->is_mmap());
     auto& mmap_region = static_cast<MmapRegion&>(*region);
+
+    // Mark the containing mmap region as a malloc block!
+    mmap_region.set_malloc(true);
+
     auto* shadow_bits = mmap_region.shadow_data() + address - mmap_region.base();
     memset(shadow_bits, 0, size);