[Driver] Pass -X to ld for riscv64-openbsd

[brad]

Summary

Noticing https://reviews.llvm.org/D127826, add support for OpenBSD which uses lld on riscv64.

[MaskRay]

Please add a test.

clang/lib/Driver/ToolChains/OpenBSD.cpp

159

isRISCV

If OpenBSD gets riscv32, it'd need -X, too.

[brad]

I will add a test.

clang/lib/Driver/ToolChains/OpenBSD.cpp

159

There is no interest in further 32-bit archs.

[brad]

Add a test.

[brad]

Minus the new white space.

[brad]

Fix the test.

[MaskRay]

clang/test/Driver/openbsd.c

133 ↗

(On Diff #438075)

It's useful to check other values like the -m emulation and the dynamic linker.

[brad]

clang/test/Driver/openbsd.c

133 ↗

(On Diff #438075)

The dynamic linker flags are tested further up in openbsd.c. The driver currently does not pass back the emulation flag.

clang/lib/Driver/ToolChains/OpenBSD.cpp

     }
   }
 
   if (Args.hasArg(options::OPT_pie))
     CmdArgs.push_back("-pie");
   if (Args.hasArg(options::OPT_nopie) || Args.hasArg(options::OPT_pg))
     CmdArgs.push_back("-nopie");
 
+  if (ToolChain.getArch() == llvm::Triple::riscv64)
+    CmdArgs.push_back("-X");
+
   if (Output.isFilename()) {
     CmdArgs.push_back("-o");
     CmdArgs.push_back(Output.getFilename());
   } else {
     assert(Output.isNothing() && "Invalid output.");
   }
 
   if (!Args.hasArg(options::OPT_nostdlib, options::OPT_nostartfiles,