Install llvm-readelf as part of -DLLVM_INSTALL_TOOLCHAIN_ONLY=ON

[arichardson]

Summary

While llvm-readobj is not part of the normal toolchain llvm-readelf is
compatible with GNU readelf and installing it can be useful.
However, I was not able to add llvm-readelf without also installing
llvm-readobj. This can probably be solved by renaming the main CMake target
to be llvm-readelf and have llvm-readobj as a symlink instead.
Should I also try to make this change to avoid installing llvm-readobj or
is the current approach fine?

[grimar]

I think we want to install both probably, so this approach looks right to me.
I'd like to hear other people opinion on that.

[jhenderson]

Yeah, I'm inclined to say we should have both too. There may be some users out there for e.g. COFF etc where people would be a bit surprised running llvm-readelf. Having both tools means we don't need to worry about which is a symlink of the other.

[arichardson]

In D82170#2103151, @jhenderson wrote:

Yeah, I'm inclined to say we should have both too. There may be some users out there for e.g. COFF etc where people would be a bit surprised running llvm-readelf. Having both tools means we don't need to worry about which is a symlink of the other.

Sounds good to me, I'll drop D82172 in that case.

llvm/cmake/modules/AddLLVM.cmake

set (LLVM_TOOLCHAIN_TOOLS
     llvm-cov
     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
     ar
     c++filt
     ranlib
     nm
     objcopy
     objdump
+    readelf
     size
     strings
     strip
     )
 endif()
 
 macro(add_llvm_tool name)
   if( NOT LLVM_BUILD_TOOLS )