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.