[HIP] Remove useless sections in linked files

[yaxunl]

Summary

clang-offload-bundler creates __CLANG_OFFLOAD_BUNDLE__* sections in the bundles,
which get into the linked files. These sections are useless after linking. They waste disk
space and cause confusion for clang when directly linked with other object files, therefore
should be removed.

lib/Driver/ToolChains/CommonArgs.cpp

void tools::AddHIPLinkerScript(const ToolChain &TC, Compilation &C,
   LksStream << "SECTIONS\n";
   LksStream << "{\n";
   LksStream << "  .hip_fatbin :\n";
   LksStream << "  ALIGN(0x10)\n";
   LksStream << "  {\n";
   LksStream << "    PROVIDE_HIDDEN(__hip_fatbin = .);\n";
   LksStream << "    " << BundleFileName << "\n";
   LksStream << "  }\n";
+  LksStream << "  /DISCARD/ :\n";
+  LksStream << "  {\n";
+  LksStream << "    * ( __CLANG_OFFLOAD_BUNDLE__* )\n";
+  LksStream << "  }\n";
   LksStream << "}\n";
   LksStream << "INSERT BEFORE .data\n";
   LksStream.flush();
 
   // Dump the contents of the linker script if the user requested that. We
   // support this option to enable testing of behavior with -###.
   if (C.getArgs().hasArg(options::OPT_fhip_dump_offload_linker_script))
     llvm::errs() << LksBuffer;