[NFC][compiler-rt] Try to collect more info about crashes on bot

Author: vitalybuka

compiler-rt/lib/lsan/lsan_common.cpp

@@ -568,6 +568,7 @@ static void ProcessRootRegions(Frontier *frontier) {
   MemoryMappingLayout proc_maps(/*cache_enabled*/ true);
   MemoryMappedSegment segment;
   InternalMmapVector<Region> mapped_regions;
+  CHECK_EQ(mapped_regions.size(), 0ull);
   while (proc_maps.Next(&segment))
     if (segment.IsReadable())
       mapped_regions.push_back({segment.start, segment.end});