Driver: libubsan_cxx depends on libubsan. Preserve the topological ordering, some linkers depend on it.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@193048 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Driver/Tools.cpp b/lib/Driver/Tools.cpp
index c85ff8d..2ab8b00 100644
--- a/lib/Driver/Tools.cpp
+++ b/lib/Driver/Tools.cpp
@@ -1779,13 +1779,14 @@
 static void addUbsanRTLinux(const ToolChain &TC, const ArgList &Args,
                             ArgStringList &CmdArgs, bool IsCXX,
                             bool HasOtherSanitizerRt) {
-  addSanitizerRTLinkFlagsLinux(TC, Args, CmdArgs, "ubsan", false, false);
-
   // Only include the bits of the runtime which need a C++ ABI library if
   // we're linking in C++ mode.
   if (IsCXX)
     addSanitizerRTLinkFlagsLinux(TC, Args, CmdArgs, "ubsan_cxx", false, false);
 
+  // Now insert the common ubsan bits. ubsan_cxx depends on them.
+  addSanitizerRTLinkFlagsLinux(TC, Args, CmdArgs, "ubsan", false, false);
+
   // Need a copy of sanitizer_common. This could come from another sanitizer
   // runtime; if we're not including one, include our own copy.
   if (!HasOtherSanitizerRt)