[Driver][FreeBSD] Further simplify the Driver handling for older FreeBSD releases

[brad]

Summary

With the last diff as I was simplifying some bits and removing FreeBSD 8 / 9 support I forgot to do this part as well.

Since GCC 4.2 was removed with 10.0 and newer the respective Driver bits can be removed.

[dim]

LGTM, are there no test cases which are affected by this?

[brad]

In D144778#4152443, @dim wrote:

LGTM, are there no test cases which are affected by this?

The stdc++ library test for FreeBSD 9 was removed in the previous diff and I don't see anything testing the header path.

clang/lib/Driver/ToolChains/FreeBSD.h

RuntimeLibType GetDefaultRuntimeLibType() const override {
     return ToolChain::RLT_CompilerRT;
   }
   CXXStdlibType GetDefaultCXXStdlibType() const override {
     return ToolChain::CST_Libcxx;
   }
 
   void addLibCxxIncludePaths(const llvm::opt::ArgList &DriverArgs,
                              llvm::opt::ArgStringList &CC1Args) const override;
-  void
-  addLibStdCxxIncludePaths(const llvm::opt::ArgList &DriverArgs,
-                           llvm::opt::ArgStringList &CC1Args) const override;
   void AddCXXStdlibLibArgs(const llvm::opt::ArgList &Args,
                            llvm::opt::ArgStringList &CmdArgs) const override;
   void AddCudaIncludeArgs(const llvm::opt::ArgList &DriverArgs,
                           llvm::opt::ArgStringList &CC1Args) const override;
   void AddHIPIncludeArgs(const llvm::opt::ArgList &DriverArgs,
                          llvm::opt::ArgStringList &CC1Args) const override;
 
   llvm::ExceptionHandling

clang/lib/Driver/ToolChains/FreeBSD.cpp

 }
 
 void FreeBSD::addLibCxxIncludePaths(const llvm::opt::ArgList &DriverArgs,
                                     llvm::opt::ArgStringList &CC1Args) const {
   addSystemInclude(DriverArgs, CC1Args,
                    concat(getDriver().SysRoot, "/usr/include/c++/v1"));
 }
 
-void FreeBSD::addLibStdCxxIncludePaths(
-    const llvm::opt::ArgList &DriverArgs,
-    llvm::opt::ArgStringList &CC1Args) const {
-  addLibStdCXXIncludePaths(concat(getDriver().SysRoot, "/usr/include/c++/4.2"),
-                           "", "", DriverArgs, CC1Args);
-}
-
 void FreeBSD::AddCXXStdlibLibArgs(const ArgList &Args,
                                   ArgStringList &CmdArgs) const {
-  CXXStdlibType Type = GetCXXStdlibType(Args);
   unsigned Major = getTriple().getOSMajorVersion();
   bool Profiling = Args.hasArg(options::OPT_pg) && Major != 0 && Major < 14;
 
-  switch (Type) {
-  case ToolChain::CST_Libcxx:
-    CmdArgs.push_back(Profiling ? "-lc++_p" : "-lc++");
-    if (Args.hasArg(options::OPT_fexperimental_library))
-      CmdArgs.push_back("-lc++experimental");
-    break;
-
-  case ToolChain::CST_Libstdcxx:
-    CmdArgs.push_back(Profiling ? "-lstdc++_p" : "-lstdc++");
-    break;
-  }
+  CmdArgs.push_back(Profiling ? "-lc++_p" : "-lc++");
+  if (Args.hasArg(options::OPT_fexperimental_library))
+    CmdArgs.push_back("-lc++experimental");
 }
 
 void FreeBSD::AddCudaIncludeArgs(const ArgList &DriverArgs,
                                  ArgStringList &CC1Args) const {
   CudaInstallation->AddCudaIncludeArgs(DriverArgs, CC1Args);
 }
 
 void FreeBSD::AddHIPIncludeArgs(const ArgList &DriverArgs,