[lldb/Module] Allow for the creation of memory-only modules

Summary:
This patch extends the ModuleSpec class to include a
DataBufferSP which contains the module data. If this
data is provided, LLDB won't try to hit the filesystem
to create the Module, but use only the data stored in
the ModuleSpec.

Reviewers: labath, espindola

Subscribers: emaste, MaskRay, lldb-commits

Tags: #lldb

Differential Revision: https://reviews.llvm.org/D83512

lldb/source/Plugins/ObjectFile/ELF/ObjectFileELF.cpp

@@ -541,7 +541,8 @@ size_t ObjectFileELF::GetModuleSpecifications(
                       __FUNCTION__, file.GetPath().c_str());
           }
 
-          data_sp = MapFileData(file, -1, file_offset);
+          if (data_sp->GetByteSize() < length)
+            data_sp = MapFileData(file, -1, file_offset);
           if (data_sp)
             data.SetData(data_sp);
           // In case there is header extension in the section #0, the header we
@@ -580,8 +581,7 @@ size_t ObjectFileELF::GetModuleSpecifications(
                   func_cat,
                   "Calculating module crc32 %s with size %" PRIu64 " KiB",
                   file.GetLastPathComponent().AsCString(),
-                  (FileSystem::Instance().GetByteSize(file) - file_offset) /
-                      1024);
+                  (length - file_offset) / 1024);
 
               // For core files - which usually don't happen to have a
               // gnu_debuglink, and are pretty bulky - calculating whole