[clang] Add linker flag when including "asan_dynamic_runtime_thunk".

[mpividori]

Summary

I need to modify clang driver for windows to include: -wholearchive:asan_dynamic_runtime_thunk, so all the object files in the static library: asan_dynamic_runtime_thunk are considered by the linker. This is necessary, because some object files only include linker pragmas, and doesn't resolve any symbol, so if we don't include that flag, the linker will ignore them, and won't read the linker pragmas.

[zturner]

seems reasonable to me, but I will let rnk@ give final lgtm.

[mpividori]

I fix a test for clang driver, that was failing with this modification.

[rnk]

lgtm

lib/Driver/Tools.cpp

if (TC.getSanitizerArgs().needsSharedAsanRt() ||
       for (const auto &Lib : {"asan_dynamic", "asan_dynamic_runtime_thunk"})
         CmdArgs.push_back(TC.getCompilerRTArgString(Args, Lib));
       // Make sure the dynamic runtime thunk is not optimized out at link time
       // to ensure proper SEH handling.
       CmdArgs.push_back(Args.MakeArgString(
           TC.getArch() == llvm::Triple::x86
               ? "-include:___asan_seh_interceptor"
               : "-include:__asan_seh_interceptor"));
+      // Make sure the linker consider all object files from the dynamic runtime
+      // thunk.
+      CmdArgs.push_back(Args.MakeArgString(std::string("-wholearchive:") +
+          TC.getCompilerRT(Args, "asan_dynamic_runtime_thunk")));
     } else if (DLL) {
       CmdArgs.push_back(TC.getCompilerRTArgString(Args, "asan_dll_thunk"));
     } else {
       for (const auto &Lib : {"asan", "asan_cxx"})
         CmdArgs.push_back(TC.getCompilerRTArgString(Args, Lib));
     }
   }