Use llvm-objcopy with StripSymbols=true and clang

[am11]

Make NativeAOT publishing adapt to changes made in #71446.

If llvm-toolchain is used for AOT compilation, the symbol stripping step will now use llvm-objcopy on Linux. Otherwise it will use binutils' (unprefixed) objcopy.

[am11]

Tested on linux-x64 with:

$ mkdir ~/.dotnet7
$ curl -sSL https://aka.ms/dotnet/7.0.1xx/daily/dotnet-sdk-linux-x64.tar.gz | tar xzf - -C ~/.dotnet7
$ cat > nuget.config << EOF
<configuration>
  <packageSources><add key="dotnet7" value="https://pkgs.dev.azure.com/dnceng/public/_packaging/dotnet7/nuget/v3/index.json" /></packageSources>
</configuration>
EOF
$ alias dotnet7=~/.dotnet7/dotnet

# overwrite the two modified files in
#   ~/.dotnet7/sdk/7.0.100-preview.7.22324.4/Sdks/Microsoft.DotNet.ILCompiler/build

$ dotnet7 new classlib -n nativelib1
$ dotnet7 publish nativelib1 -o dist -c Release --use-current-runtime -p:PublishAot=true -p:StripSymbols=true
$ ls -la dist

total 14496
drwxrwxr-x 2 am11 am11     4096 Jun 30 19:58 .
drwxrwxr-x 5 am11 am11     4096 Jun 30 19:58 ..
-rwxrwxr-x 1 am11 am11  4587888 Jun 30 19:58 nativelib1.so
-rwxrwxr-x 1 am11 am11 10240432 Jun 30 19:58 nativelib1.so.dbg

(without -p:StripSymbols=true .dbg file is not produced and nativelib1.so size is enlarges)

[janvorli]

How about the version suffix? On my Linux devbox, I don't have any version of llvm tools (including clang) without the suffix.

[am11]

This is a good point.

Currently, with auto-detection, we only support toolchain selection without the version suffix in NativeAOT. On Ubuntu, for example, when we install clang/llvm from package manager, it installs a package called llvm-defaults, which installs llvm-objcopy (along other tools) in /usr/bin:

$ command -v llvm-objcopy
/usr/bin/llvm-objcopy

However, for versioned clang or gcc user can set a property -p:CppCompilerAndLinker=clang-10, but for objcopy, we don't have it.

I can add support to set ObjCopyName property externally similar to CppCompilerAndLinker. But I think it is better if we implement the complete autodetection properly (by packaging init-compiler.sh). That is in my TODO list. :)

[jkotas]

I can add support to set ObjCopyName property externally similar to CppCompilerAndLinker

Yes, that would be good. We should always have an option to explicitly control these names and override what the auto-detection thinks.

[janvorli]

@am11 Thank you for the details, that makes sense. Let's keep this change as is and implement the version detection separately.

[janvorli]

Modulo @jkotas's comment, so let's add the ObjCopyName

[am11]

I have changed it so it is set conditionally. -p:ObjCopyName=llvm-objcopy-10 or -p:ObjCopyName=/path/to/llvm-objcopy.

[janvorli]

LGTM, thank you!

[jkotas]

The test failure is Helix timeout - the test succeeded.