[elf] Remove one copy of the section merging code

[labath]

Summary

Besides being superfluous, this double merging was actually wrong and
causing some sections to be added twice. The reason for that was that
the code assumes sectoin IDs are unique in the section list, but this is
only true if all sections in the list come from the same object file.

[jankratochvil]

Yes, it should be the same I think; some notes of mine:

Module::GetSectionList()->obj_file->CreateSections(*GetUnifiedSectionList());
        Module::GetUnifiedSectionList()->Module::m_sections_ap.get();

ObjectFileELF::CreateSections()->removal
        ObjectFileELF::m_sections_ap.get() ---> Module::m_sections_ap.get();

SymbolVendorELF::CreateInstance()
        ObjectFileSP dsym_objfile_sp->SetType(ObjectFile::eTypeDebugInfo);
        SymbolVendorELF *symbol_vendor = new SymbolVendorELF(module_sp);
        dsym_objfile_sp->GetSectionList(); ---> module_sp->GetSectionList();

lit/Modules/elf-duplicate-section.yaml

+# RUN: mkdir -p %t/.build-id/1b
+# RUN: yaml2obj %s > %t/.build-id/1b/8a73ac238390e32a7ff4ac8ebe4d6a41ecf5c9.debug
+# RUN: cd %t
+# RUN: llvm-objcopy --strip-all --add-gnu-debuglink=.build-id/1b/8a73ac238390e32a7ff4ac8ebe4d6a41ecf5c9.debug %t/.build-id/1b/8a73ac238390e32a7ff4ac8ebe4d6a41ecf5c9.debug %t/stripped.out
+# RUN: lldb-test module-sections %t/stripped.out | FileCheck %s
+
+# Make sure that the debug_frame section is present only once.
+# CHECK: Name: .debug_frame
+# CHECK-NOT: .debug_frame
+
+--- !ELF
+FileHeader:
+  Class:           ELFCLASS64
+  Data:            ELFDATA2LSB
+  Type:            ET_EXEC
+  Machine:         EM_X86_64
+  Entry:           0x00000000004003D0
+Sections:
+  - Name:            .note.gnu.build-id
+    Type:            SHT_NOTE
+    Flags:           [ SHF_ALLOC ]
+    Address:         0x0000000000400274
+    AddressAlign:    0x0000000000000004
+    Content:         040000001400000003000000474E55001B8A73AC238390E32A7FF4AC8EBE4D6A41ECF5C9
+  - Name:            .text
+    Type:            SHT_PROGBITS
+    Flags:           [ SHF_ALLOC, SHF_EXECINSTR ]
+    Address:         0x00000000004003D0
+    AddressAlign:    0x0000000000000010
+    Content:         DEADBEEFBAADF00D
+  - Name:            .debug_frame
+    Type:            SHT_PROGBITS
+    AddressAlign:    0x0000000000000008
+    Content:         DEADBEEFBAADF00D
+Symbols:
+  Local:
+    - Name:            main
+      Type:            STT_FUNC
+      Section:         .text
+      Value:           0x00000000004003D0
+      Size:            0x0000000000000008
+...

source/Plugins/ObjectFile/ELF/ObjectFileELF.cpp

for (SectionHeaderCollIter I = m_section_headers.begin();
 
       section_sp->SetPermissions(permissions);
       if (is_thread_specific)
         section_sp->SetIsThreadSpecific(is_thread_specific);
       m_sections_ap->AddSection(section_sp);
     }
   }
 
-  if (m_sections_ap.get()) {
-    if (GetType() == eTypeDebugInfo) {
-      static const SectionType g_sections[] = {
-          eSectionTypeDWARFDebugAbbrev,   eSectionTypeDWARFDebugAddr,
-          eSectionTypeDWARFDebugAranges,  eSectionTypeDWARFDebugCuIndex,
-          eSectionTypeDWARFDebugFrame,    eSectionTypeDWARFDebugInfo,
-          eSectionTypeDWARFDebugLine,     eSectionTypeDWARFDebugLoc,
-          eSectionTypeDWARFDebugMacInfo,  eSectionTypeDWARFDebugPubNames,
-          eSectionTypeDWARFDebugPubTypes, eSectionTypeDWARFDebugRanges,
-          eSectionTypeDWARFDebugStr,      eSectionTypeDWARFDebugStrOffsets,
-          eSectionTypeELFSymbolTable,
-      };
-      SectionList *elf_section_list = m_sections_ap.get();
-      for (size_t idx = 0; idx < sizeof(g_sections) / sizeof(g_sections[0]);
-           ++idx) {
-        SectionType section_type = g_sections[idx];
-        SectionSP section_sp(
-            elf_section_list->FindSectionByType(section_type, true));
-        if (section_sp) {
-          SectionSP module_section_sp(
-              unified_section_list.FindSectionByType(section_type, true));
-          if (module_section_sp)
-            unified_section_list.ReplaceSection(module_section_sp->GetID(),
-                                                section_sp);
-          else
-            unified_section_list.AddSection(section_sp);
-        }
-      }
-    } else {
-      unified_section_list = *m_sections_ap;
-    }
-  }
-}
+  // For eTypeDebugInfo files, the Symbol Vendor will take care of updating the
+  // unified section list.
+  if (GetType() != eTypeDebugInfo)
 
 // Find the arm/aarch64 mapping symbol character in the given symbol name.
 // Mapping symbols have the
 // form of "$<char>[.<any>]*". Additionally we recognize cases when the mapping
 // symbol prefixed by
 // an arbitrary string because if a symbol prefix added to each symbol in the
 // object file with
 // objcopy then the mapping symbols are also prefixed.