Enable dead stripping of NativeAOT executables on Apple platforms

Author: ivanpovazan

src/coreclr/nativeaot/BuildIntegration/Microsoft.NETCore.Native.targets

@@ -341,6 +341,7 @@ The .NET Foundation licenses this file to you under the MIT license.
       <CustomLinkerArg Include="-exported_symbols_list /dev/null" Condition="'$(OutputType)' == 'exe' and '$(_IsApplePlatform)' == 'true' and '$(ExportsFile)' == ''" />
       <CustomLinkerArg Include="-Wl,--version-script=$(ExportsFile)" Condition="'$(_targetOS)' != 'win' and '$(_IsApplePlatform)' != 'true' and '$(ExportsFile)' != ''" />
       <CustomLinkerArg Include="-Wl,--export-dynamic" Condition="'$(_targetOS)' != 'win' and '$(_IsApplePlatform)' != 'true' and '$(ExportsFile)' != ''" />
+      <CustomLinkerArg Include="-Wl,-dead_strip" Condition="'$(_IsApplePlatform)' == 'true'" />
       <CustomLinkerArg Include="@(LinkerArg)" />
     </ItemGroup>
     <ItemGroup Condition="'$(_targetOS)' != 'win' and '$(_IsApplePlatform)' != 'true'">

src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/ObjectWriter/MachObjectWriter.cs

@@ -475,12 +475,15 @@ private protected override void EmitSymbolTable(
             foreach ((string name, SymbolDefinition definition) in definedSymbols)
             {
                 MachSection section = _sections[definition.SectionIndex];
+                // Sections in our object file should not be altered during native linking as the runtime
+                // depends on the layout generated during compilation. For this reason we mark all symbols
+                // with N_NO_DEAD_STRIP to prevent breaking up sections into subsections during linking.
                 sortedDefinedSymbols.Add(new MachSymbol
                 {
                     Name = name,
                     Section = section,
                     Value = section.VirtualAddress + (ulong)definition.Value,
-                    Descriptor = 0,
+                    Descriptor = N_NO_DEAD_STRIP,
                     Type = N_SECT | N_EXT,
                 });
             }