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

[brad]

Summary

Similar to D116843.

[MaskRay]

Thanks!

clang/lib/Driver/ToolChains/Minix.cpp

void tools::minix::Linker::ConstructJob(Compilation &C, const JobAction &JA,
 
   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)) {
+  if (!Args.hasArg(options::OPT_nostdlib, options::OPT_nostartfiles,
+                   options::OPT_r)) {
     CmdArgs.push_back(Args.MakeArgString(getToolChain().GetFilePath("crt1.o")));
     CmdArgs.push_back(Args.MakeArgString(getToolChain().GetFilePath("crti.o")));
     CmdArgs.push_back(
         Args.MakeArgString(getToolChain().GetFilePath("crtbegin.o")));
     CmdArgs.push_back(Args.MakeArgString(getToolChain().GetFilePath("crtn.o")));
   }
 
   Args.AddAllArgs(CmdArgs,
                   {options::OPT_L, options::OPT_T_Group, options::OPT_e});
 
   AddLinkerInputs(getToolChain(), Inputs, Args, CmdArgs, JA);
 
   getToolChain().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 (D.CCCIsCXX()) {
       if (getToolChain().ShouldLinkCXXStdlib(Args))
         getToolChain().AddCXXStdlibLibArgs(Args, CmdArgs);
       CmdArgs.push_back("-lm");
     }
   }
 
-  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_pthread))
       CmdArgs.push_back("-lpthread");
     CmdArgs.push_back("-lc");
     CmdArgs.push_back("-lCompilerRT-Generic");
     CmdArgs.push_back("-L/usr/pkg/compiler-rt/lib");
     CmdArgs.push_back(
         Args.MakeArgString(getToolChain().GetFilePath("crtend.o")));
   }

clang/test/Driver/minix.c

+// -r suppresses default -l and crt*.o like -nostdlib.
+// RUN: %clang -### %s --target=i386-unknown-minix -r 2>&1 \
+// RUN:   | FileCheck %s --check-prefix=CHECK-RELOCATABLE
+// CHECK-RELOCATABLE:     "-r"
+// CHECK-RELOCATABLE-NOT: "-l
+// CHECK-RELOCATABLE-NOT: /crt{{[^.]+}}.o