Re-enable gc-sections with lld for NativeAOT (#84935)

* Revert "Revert "Write linker script for lld to enable gc-sections (#84493)""

This reverts the revert of commit 3ab663e.
The revert of that commit was included in 887c043.

* Lower the lld version requirement

* Adjust dwarfdump baseline

---------

Co-authored-by: Adeel <3840695+am11@users.noreply.github.com>

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

@@ -181,6 +181,15 @@ The .NET Foundation licenses this file to you under the MIT license.
     <Error Condition="'$(_WhereLinker)' != '0' and '$(CppCompilerAndLinkerAlternative)' == '' and '$(_IsApplePlatform)' != 'true'"
       Text="Requested linker ('$(CppLinker)') not found in PATH." />
 
+    <Exec Command="&quot;$(CppLinker)&quot; -fuse-ld=lld -Wl,--version" Condition="'$(LinkerFlavor)' == 'lld'" IgnoreExitCode="true" StandardOutputImportance="Low" ConsoleToMSBuild="true">
+      <Output TaskParameter="ExitCode" PropertyName="_LinkerVersionStringExitCode" />
+      <Output TaskParameter="ConsoleOutput" PropertyName="_LinkerVersionString" />
+    </Exec>
+
+    <PropertyGroup Condition="'$(_LinkerVersionStringExitCode)' == '0' and '$(_LinkerVersionString)' != ''">
+      <_LinkerVersion>$([System.Text.RegularExpressions.Regex]::Match($(_LinkerVersionString), '[1-9]\d*'))</_LinkerVersion>
+    </PropertyGroup>
+
     <Exec Command="command -v &quot;$(ObjCopyName)&quot;" IgnoreExitCode="true" StandardOutputImportance="Low" Condition="'$(_IsApplePlatform)' != 'true' and '$(StripSymbols)' == 'true'">
       <Output TaskParameter="ExitCode" PropertyName="_WhereSymbolStripper" />
     </Exec>

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

@@ -318,7 +318,8 @@ The .NET Foundation licenses this file to you under the MIT license.
     </ItemGroup>
     <ItemGroup Condition="'$(_targetOS)' != 'win' and '$(_IsApplePlatform)' != 'true'">
       <CustomLinkerArg Include="-Wl,--discard-all" />
-      <CustomLinkerArg Include="-Wl,--gc-sections" Condition="'$(LinkerFlavor)' == '' or '$(LinkerFlavor)' == 'bfd'" />
+      <CustomLinkerArg Include="-Wl,--gc-sections" Condition="'$(LinkerFlavor)' == '' or '$(LinkerFlavor)' == 'bfd' or '$(LinkerFlavor)' == 'lld'" />
+      <CustomLinkerArg Include="-Wl,-T,&quot;$(NativeIntermediateOutputPath)sections.ld&quot;" Condition="'$(LinkerFlavor)' == 'lld' and '$(_LinkerVersion)' &gt; '12'" />
     </ItemGroup>
     <ItemGroup>
       <CustomLibArg Include="-crs &quot;$(NativeBinary)&quot;" Condition="'$(_targetOS)' != 'win'" />
@@ -335,6 +336,9 @@ The .NET Foundation licenses this file to you under the MIT license.
       <StripFlag Condition="'$(_IsApplePlatform)' == 'true' and '$(NativeLib)' == 'Shared'">-x</StripFlag> <!-- keep global symbols in dylib -->
     </PropertyGroup>
 
+    <!-- write linker script for lld (13+) to retain the __modules section -->
+    <WriteLinesToFile File="$(NativeIntermediateOutputPath)sections.ld" Lines="OVERWRITE_SECTIONS { __modules : { KEEP(*(__modules)) } }" Overwrite="true" Condition="'$(LinkerFlavor)' == 'lld' and '$(_LinkerVersion)' &gt; '12'" />
+
     <Exec Command="&quot;$(CppLinker)&quot; @(CustomLinkerArg, ' ')" Condition="'$(_targetOS)' != 'win' and '$(NativeLib)' != 'Static'" IgnoreStandardErrorWarningFormat="$(_IgnoreLinkerWarnings)" />
     <Exec Command="&quot;$(CppLibCreator)&quot; @(CustomLibArg, ' ')" Condition="'$(_targetOS)' != 'win' and '$(NativeLib)' == 'Static'" />
 

src/tests/nativeaot/SmokeTests/DwarfDump/Program.cs

@@ -54,8 +54,8 @@ public static int Main(string[] args)
         const int MinWarnings = 16500;
         const int MaxWarnings = 18500;
 #else
-        const int MinWarnings = 9500;
-        const int MaxWarnings = 10500;
+        const int MinWarnings = 12000;
+        const int MaxWarnings = 13000;
 #endif
         int count = 0;
         string line;