Install llvm-readelf instead of llvm-readobj

[arichardson]

Summary

I would like to install llvm-readelf as part of a toolchain install
with -DLLVM_INSTALL_TOOLCHAIN_ONLY=ON. However, llvm-readelf is currently
a symlink to llvm-readobj. llvm-readelf uses the GNU compatible output
style, whereas llvm-readobj is mostly used for testing.
This commit changes llvm-readobj to be a symlink to llvm-readelf so we can
create a -DLLVM_INSTALL_TOOLCHAIN_ONLY=ON installation that has a readelf
binary but does not include llvm-readobj.

See D82170

[MaskRay]

Looks good (llvm-readobj is very rarely used outside LLVM, while llvm-readelf is more common as a replacement of GNU readelf)

[MaskRay]

LGTM, but this needs to fix lld: error: undefined symbol: llvm_readelf_main(int, char**, llvm::ToolContext const&)

[jhenderson]

LGTM too, pending @MaskRay's requested fix.

[arichardson]

Thanks for the review, totally forgot about this patch. Will update and submit once the multicall driver error had been fixed.

llvm/cmake/modules/AddLLVM.cmake

set (LLVM_TOOLCHAIN_TOOLS
     llvm-cxxfilt
     llvm-ranlib
     llvm-lib
     llvm-nm
     llvm-objcopy
     llvm-objdump
     llvm-rc
     llvm-readelf
-    llvm-readobj
     llvm-size
     llvm-strings
     llvm-strip
     llvm-profdata
     llvm-symbolizer
     # symlink version of some of above tools that are enabled by
     # LLVM_INSTALL_BINUTILS_SYMLINKS.
     addr2line

llvm/tools/llvm-readobj/CMakeLists.txt

 set(LLVM_LINK_COMPONENTS
   DebugInfoCodeView
   DebugInfoDWARF
   Demangle
   Object
   BinaryFormat
   Support
   DebugInfoCodeView
   DebugInfoMSF
   DebugInfoPDB
   )
 
-add_llvm_tool(llvm-readobj
+add_llvm_tool(llvm-readelf
   ARMWinEHPrinter.cpp
   COFFDumper.cpp
   COFFImportDumper.cpp
   ELFDumper.cpp
   Error.cpp
   llvm-readobj.cpp
   MachODumper.cpp
   ObjDumper.cpp
   WasmDumper.cpp
   Win64EHDumper.cpp
   WindowsResourceDumper.cpp
   XCOFFDumper.cpp
   )
 
-add_llvm_tool_symlink(llvm-readelf llvm-readobj)
+add_llvm_tool_symlink(llvm-readobj llvm-readelf)
 
 if(LLVM_INSTALL_BINUTILS_SYMLINKS)
-  add_llvm_tool_symlink(readelf llvm-readobj)
+  add_llvm_tool_symlink(readelf llvm-readelf)
 endif()