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

[brad]

Summary

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

[MaskRay]

Looks good if Fuchsia wants to match

[phosek]

LGTM

clang/lib/Driver/ToolChains/Fuchsia.cpp

if (SanArgs.needsHwasanRt() && SanArgs.needsSharedRt())
       Dyld += "hwasan/";
     if (SanArgs.needsTsanRt() && SanArgs.needsSharedRt())
       Dyld += "tsan/";
     Dyld += "ld.so.1";
     CmdArgs.push_back("-dynamic-linker");
     CmdArgs.push_back(Args.MakeArgString(Dyld));
   }
 
+  if (ToolChain.getArch() == llvm::Triple::riscv64)
+    CmdArgs.push_back("-X");
+
   CmdArgs.push_back("-o");
   CmdArgs.push_back(Output.getFilename());
 
   if (!Args.hasArg(options::OPT_nostdlib, options::OPT_nostartfiles,
                    options::OPT_r)) {
     if (!Args.hasArg(options::OPT_shared)) {
       CmdArgs.push_back(Args.MakeArgString(ToolChain.GetFilePath("Scrt1.o")));
     }

clang/test/Driver/fuchsia.c

 // CHECK-NOT: "-fcommon"
 // CHECK: {{.*}}ld.lld{{.*}}" "-z" "max-page-size=4096" "-z" "now" "-z" "rodynamic" "-z" "separate-loadable-segments" "-z" "rel" "--pack-dyn-relocs=relr"
 // CHECK: "--sysroot=[[SYSROOT]]"
 // CHECK: "-pie"
 // CHECK: "--build-id"
 // CHECK: "--hash-style=gnu"
 // CHECK-AARCH64: "--fix-cortex-a53-843419"
 // CHECK: "-dynamic-linker" "ld.so.1"
+// CHECK-RISCV64: "-X"
 // CHECK: Scrt1.o
 // CHECK-NOT: crti.o
 // CHECK-NOT: crtbegin.o
 // CHECK: "-L[[SYSROOT]]{{/|\\\\}}lib"
 // CHECK-X86_64: "[[RESOURCE_DIR]]{{/|\\\\}}lib{{/|\\\\}}x86_64-unknown-fuchsia{{/|\\\\}}libclang_rt.builtins.a"
 // CHECK-AARCH64: "[[RESOURCE_DIR]]{{/|\\\\}}lib{{/|\\\\}}aarch64-unknown-fuchsia{{/|\\\\}}libclang_rt.builtins.a"
 // CHECK-RISCV64: "[[RESOURCE_DIR]]{{/|\\\\}}lib{{/|\\\\}}riscv64-unknown-fuchsia{{/|\\\\}}libclang_rt.builtins.a"
 // CHECK: "-lc"