This patch makes clang default to DWARF2 debug info format for FreeBSD
10.x and earlier.

Introduced here: http://svnweb.freebsd.org/changeset/base/263891

Index: tools/clang/lib/Driver/Tools.cpp
===================================================================
--- tools/clang/lib/Driver/Tools.cpp
+++ tools/clang/lib/Driver/Tools.cpp
@@ -2628,8 +2628,10 @@ void Clang::ConstructJob(Compilation &C, const Job
       CmdArgs.push_back("-gdwarf-4");
     else if (!A->getOption().matches(options::OPT_g0) &&
              !A->getOption().matches(options::OPT_ggdb0)) {
-      // Default is dwarf-2 for darwin.
-      if (getToolChain().getTriple().isOSDarwin())
+      // Default is dwarf-2 for darwin and FreeBSD <= 10.
+      const llvm::Triple &Triple = getToolChain().getTriple();
+      if (Triple.isOSDarwin() || (Triple.getOS() == llvm::Triple::FreeBSD &&
+          Triple.getOSMajorVersion() <= 10))
         CmdArgs.push_back("-gdwarf-2");
       else
         CmdArgs.push_back("-g");