[Driver] move DragonFly header search path management to the driver

As has been done for other OS's. Move the header path management to the driver.

Also I noticed with D89690 that the library paths were updated for GCC 8, but
the C++ header path was not. So I also fixed that while here.

Reviewed By: MaskRay

Differential Revision: https://reviews.llvm.org/D158376

Author: brad0

clang/lib/Driver/ToolChains/DragonFly.cpp

@@ -12,6 +12,7 @@
 #include "clang/Driver/Driver.h"
 #include "clang/Driver/Options.h"
 #include "llvm/Option/ArgList.h"
+#include "llvm/Support/Path.h"
 
 using namespace clang::driver;
 using namespace clang::driver::tools;
@@ -195,6 +196,33 @@ DragonFly::DragonFly(const Driver &D, const llvm::Triple &Triple,
   getFilePaths().push_back("/usr/lib/gcc80");
 }
 
+void DragonFly::AddClangSystemIncludeArgs(
+    const llvm::opt::ArgList &DriverArgs,
+    llvm::opt::ArgStringList &CC1Args) const {
+  const Driver &D = getDriver();
+
+  if (DriverArgs.hasArg(clang::driver::options::OPT_nostdinc))
+    return;
+
+  if (!DriverArgs.hasArg(options::OPT_nobuiltininc)) {
+    SmallString<128> Dir(D.ResourceDir);
+    llvm::sys::path::append(Dir, "include");
+    addSystemInclude(DriverArgs, CC1Args, Dir.str());
+  }
+
+  if (DriverArgs.hasArg(options::OPT_nostdlibinc))
+    return;
+
+  addExternCSystemInclude(DriverArgs, CC1Args,
+                          concat(D.SysRoot, "/usr/include"));
+}
+
+void DragonFly::addLibStdCxxIncludePaths(const llvm::opt::ArgList &DriverArgs,
+                                         llvm::opt::ArgStringList &CC1Args) const {
+  addLibStdCXXIncludePaths(concat(getDriver().SysRoot, "/usr/include/c++/8.0"), "", "",
+                           DriverArgs, CC1Args);
+}
+
 Tool *DragonFly::buildAssembler() const {
   return new tools::dragonfly::Assembler(*this);
 }

clang/lib/Driver/ToolChains/DragonFly.h

@@ -55,6 +55,13 @@ class LLVM_LIBRARY_VISIBILITY DragonFly : public Generic_ELF {
 
   bool IsMathErrnoDefault() const override { return false; }
 
+  void
+  AddClangSystemIncludeArgs(const llvm::opt::ArgList &DriverArgs,
+                            llvm::opt::ArgStringList &CC1Args) const override;
+  void addLibStdCxxIncludePaths(
+      const llvm::opt::ArgList &DriverArgs,
+      llvm::opt::ArgStringList &CC1Args) const override;
+
 protected:
   Tool *buildAssembler() const override;
   Tool *buildLinker() const override;

clang/lib/Lex/InitHeaderSearch.cpp

@@ -307,9 +307,6 @@ void InitHeaderSearch::AddDefaultCPlusPlusIncludePaths(
       break;
     }
     break;
-  case llvm::Triple::DragonFly:
-    AddPath("/usr/include/c++/5.0", CXXSystem, false);
-    break;
   default:
     break;
   }
@@ -319,6 +316,7 @@ bool InitHeaderSearch::ShouldAddDefaultIncludePaths(
     const llvm::Triple &triple) {
   switch (triple.getOS()) {
   case llvm::Triple::AIX:
+  case llvm::Triple::DragonFly:
   case llvm::Triple::ELFIAMCU:
   case llvm::Triple::Emscripten:
   case llvm::Triple::FreeBSD: