[Clang] Add tools needed by Supersize to the llvmobjdump package.

This CL adds the following to llvmobjdump-$REV.tgz:
- {llvm-cxxfilt, llvm-nm, llvm-objdump, llvm-readobj},
- If non-Windows, sym link llvm-readelf -> llvm-readobj.
These are needed by Supersize to process LLD builds.

We didn't add symlink llvm-c++filt -> llvm-cxxfilt because that's not
built by default.

Next steps:
- Rebuild package and upload (or wait for next push).
- Update Supersize to look for the package by default (if needed),
  and download accordingly.

Bug: 723798
Change-Id: I1991f6aee1e51e9ce9ac61faea97660cc40f640a
Reviewed-on: https://chromium-review.googlesource.com/763728Reviewed-by: Hans Wennborg <hans@chromium.org>
Commit-Queue: Samuel Huang <huangs@chromium.org>
Cr-Commit-Position: refs/heads/master@{#515803}

tools/clang/scripts/package.py

@@ -337,12 +337,15 @@ def main():
             filter=PrintTarProgress)
   MaybeUpload(args, code_coverage_dir, platform)
 
-  # Zip up llvm-objdump for sanitizer coverage.
+  # Zip up llvm-objdump and related tools for sanitizer coverage and Supersize.
   objdumpdir = 'llvmobjdump-' + stamp
   shutil.rmtree(objdumpdir, ignore_errors=True)
   os.makedirs(os.path.join(objdumpdir, 'bin'))
-  shutil.copy(os.path.join(LLVM_RELEASE_DIR, 'bin', 'llvm-objdump' + exe_ext),
-              os.path.join(objdumpdir, 'bin'))
+  for filename in ['llvm-cxxfilt', 'llvm-nm', 'llvm-objdump', 'llvm-readobj']:
+    shutil.copy(os.path.join(LLVM_RELEASE_DIR, 'bin', filename + exe_ext),
+                os.path.join(objdumpdir, 'bin'))
+  if sys.platform != 'win32':
+    os.symlink('llvm-readobj', os.path.join(objdumpdir, 'bin', 'llvm-readelf'))
   with tarfile.open(objdumpdir + '.tgz', 'w:gz') as tar:
     tar.add(os.path.join(objdumpdir, 'bin'), arcname='bin',
             filter=PrintTarProgress)