Enable ICF on Linux (#129762)

It saves on average 2% in size.

---------

Co-authored-by: Adeel Mujahid <3840695+am11@users.noreply.github.com>
Co-authored-by: Jan Kotas <jkotas@microsoft.com>

Author: 3 people

eng/native/configurecompiler.cmake

@@ -759,6 +759,9 @@ if (CLR_CMAKE_HOST_UNIX OR CLR_CMAKE_HOST_WASI)
     add_linker_flag(-Wl,-dead_strip CHECKED RELEASE RELWITHDEBINFO)
   elseif(NOT LD_SOLARIS)
     add_linker_flag(-Wl,--gc-sections CHECKED RELEASE RELWITHDEBINFO)
+    if (NOT LD_GNU AND NOT CLR_CMAKE_TARGET_ARCH_WASM)
+      add_linker_flag(-Wl,--icf=all RELEASE RELWITHDEBINFO)
+    endif()
   endif()
 
   # Specify the minimum supported version of macOS

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

@@ -305,6 +305,7 @@ The .NET Foundation licenses this file to you under the MIT license.
       <LinkerArg Include="@(ExtraLinkerArg->'-Wl,%(Identity)')" />
       <LinkerArg Include="@(NativeFramework->'-framework %(Identity)')" Condition="'$(_IsApplePlatform)' == 'true'" />
       <LinkerArg Include="-Wl,--eh-frame-hdr" Condition="'$(_IsApplePlatform)' != 'true'" />
+      <LinkerArg Include="-Wl,--icf=all" Condition="'$(_IsApplePlatform)' != 'true' and '$(LinkerFlavor)' != 'bfd'" />
 
       <!-- Google requires all the native libraries to be aligned to 16 bytes (for 16k memory page size)
            This is required only for 64-bit binaries.