[Driver] Support PowerPC SPE musl dynamic linker name ld-musl-powerpc-sf.so.1

[pattop]

Summary

Musl treats PowerPC SPE as a soft-float target (as the PowerPC SPE ABI
is soft-float compatible).

[pattop]

Here is the corresponding gcc patch:

https://github.com/richfelker/musl-cross-make/commit/5b405688ee23df621e5b33911e2aa7b046ef632e

[nemanjai]

I personally don't see anything wrong with this, but then again I am not really familiar with SPE. I'll defer to @jhibbits for the approval.

[jhibbits]

Looks fine to me. @nemanjai this one is more Musl, less SPE :)

[MaskRay]

This needs a test like clang/test/Driver/linux-ld.c CHECK-MUSL-PPC. Use ninja check-clang-driver to test.

[pattop]

Add test case.

[MaskRay]

I have confirmed that this matches musl #define FP_SUFFIX "-sf"

clang/lib/Driver/ToolChains/Linux.cpp

case llvm::Triple::x86_64:
       break;
     default:
       ArchName = Triple.getArchName().str();
     }
     if (IsArm &&
         (Triple.getEnvironment() == llvm::Triple::MuslEABIHF ||
          tools::arm::getARMFloatABI(*this, Args) == tools::arm::FloatABI::Hard))
       ArchName += "hf";
+    if (Arch == llvm::Triple::ppc &&
+        Triple.getSubArch() == llvm::Triple::PPCSubArch_spe)
+      ArchName = "powerpc-sf";
 
     return "/lib/ld-musl-" + ArchName + ".so.1";
   }
 
   std::string LibDir;
   std::string Loader;
 
   switch (Arch) {