[Driver][Fuchsia] -r: imply -nostdlib like GCC

[MaskRay]

Summary

Similar to D116843.

[MaskRay]

This is a similar patch:)

[phosek]

Thank you! I was going to send the same change but you beat me to it.

clang/lib/Driver/ToolChains/Fuchsia.cpp

if (!Args.hasArg(options::OPT_shared)) {
     Dyld += "ld.so.1";
     CmdArgs.push_back("-dynamic-linker");
     CmdArgs.push_back(Args.MakeArgString(Dyld));
   }
 
   CmdArgs.push_back("-o");
   CmdArgs.push_back(Output.getFilename());
 
-  if (!Args.hasArg(options::OPT_nostdlib, options::OPT_nostartfiles)) {
+  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")));
     }
   }
 
   Args.AddAllArgs(CmdArgs, options::OPT_L);
   Args.AddAllArgs(CmdArgs, options::OPT_u);
 
   ToolChain.AddFilePathLibArgs(Args, CmdArgs);
 
   if (D.isUsingLTO()) {
     assert(!Inputs.empty() && "Must have at least one input.");
     addLTOOptions(ToolChain, Args, CmdArgs, Output, Inputs[0],
                   D.getLTOMode() == LTOK_Thin);
   }
 
   bool NeedsSanitizerDeps = addSanitizerRuntimes(ToolChain, Args, CmdArgs);
   bool NeedsXRayDeps = addXRayRuntime(ToolChain, Args, CmdArgs);
   AddLinkerInputs(ToolChain, Inputs, Args, CmdArgs, JA);
   ToolChain.addProfileRTLibs(Args, CmdArgs);
 
-  if (!Args.hasArg(options::OPT_nostdlib, options::OPT_nodefaultlibs)) {
+  if (!Args.hasArg(options::OPT_nostdlib, options::OPT_nodefaultlibs,
+                   options::OPT_r)) {
     if (Args.hasArg(options::OPT_static))
       CmdArgs.push_back("-Bdynamic");
 
     if (D.CCCIsCXX()) {
       if (ToolChain.ShouldLinkCXXStdlib(Args)) {
         bool OnlyLibstdcxxStatic = Args.hasArg(options::OPT_static_libstdcxx) &&
                                    !Args.hasArg(options::OPT_static);
         CmdArgs.push_back("--push-state");

clang/test/Driver/fuchsia.c

 // CHECK-SHARED-NOT: "-pie"
 // CHECK-SHARED: "-shared"
 
 // RUN: %clang %s -### --target=x86_64-unknown-fuchsia -r -fuse-ld=lld 2>&1 \
 // RUN:     | FileCheck %s -check-prefix=CHECK-RELOCATABLE
 // CHECK-RELOCATABLE-NOT: "-pie"
 // CHECK-RELOCATABLE-NOT: "--build-id"
 // CHECK-RELOCATABLE: "-r"
+// CHECK-RELOCATABLE-NOT: "-l
+// CHECK-RELOCATABLE-NOT: crt{{[^.]+}}.o
 
 // RUN: %clang %s -### --target=x86_64-unknown-fuchsia -nodefaultlibs -fuse-ld=lld 2>&1 \
 // RUN:     -resource-dir=%S/Inputs/resource_dir_with_per_target_subdir \
 // RUN:     | FileCheck %s -check-prefix=CHECK-NODEFAULTLIBS
 // CHECK-NODEFAULTLIBS: "-resource-dir" "[[RESOURCE_DIR:[^"]+]]"
 // CHECK-NODEFAULTLIBS-NOT: "[[RESOURCE_DIR]]{{/|\\\\}}lib{{/|\\\\}}x86_64-unknown-fuchsia{{/|\\\\}}libclang_rt.builtins.a"
 // CHECK-NODEFAULTLIBS-NOT: "-lc"