[Hexagon] Don't clear libpath when target is linux-musl

[sidneym]

Summary

Use the default libpath when the target is linux-musl

[bcain]

Seems like we might want a new test case for this?

clang/lib/Driver/ToolChains/Hexagon.cpp

HexagonToolChain::HexagonToolChain(const Driver &D, const llvm::Triple &Triple,
   // Note: Generic_GCC::Generic_GCC adds InstalledDir and getDriver().Dir to
   // program paths
   const std::string BinDir(TargetDir + "/bin");
   if (D.getVFS().exists(BinDir))
     getProgramPaths().push_back(BinDir);
 
   ToolChain::path_list &LibPaths = getFilePaths();
 
-  // Remove paths added by Linux toolchain. Currently Hexagon_TC really targets
-  // 'elf' OS type, so the Linux paths are not appropriate. When we actually
-  // support 'linux' we'll need to fix this up
+  if (!Triple.isMusl()) {
     LibPaths.clear();
     getHexagonLibraryPaths(Args, LibPaths);
   }
+}
 
 HexagonToolChain::~HexagonToolChain() {}
 
 Tool *HexagonToolChain::buildAssembler() const {
   return new tools::hexagon::Assembler(*this);
 }
 
 Tool *HexagonToolChain::buildLinker() const {