Implement order-preserving option forwarding.

Needed to correctly handle things like 'llvmc -framework Foo foo.o -framework
Bar bar.o' - before this commit all '-framework' options would've been grouped
together in the beginning.

Due to our dependence on CommandLine this turned out to be a giant hack; we will
migrate away from CommandLine eventually.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@96922 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CompilerDriver/Tool.cpp

@@ -17,6 +17,8 @@
 #include "llvm/ADT/StringExtras.h"
 #include "llvm/System/Path.h"
 
+#include <algorithm>
+
 using namespace llvm;
 using namespace llvmc;
 
@@ -72,11 +74,21 @@ sys::Path Tool::OutFilename(const sys::Path& In,
   return Out;
 }
 
+namespace {
+  template <class A, class B>
+  bool CompareFirst (std::pair<A,B> p1, std::pair<A,B> p2) {
+    return std::less<A>()(p1.first, p2.first);
+  }
+}
+
 StrVector Tool::SortArgs(ArgsVector& Args) const {
   StrVector Out;
 
-  for (ArgsVector::iterator B = Args.begin(), E = Args.end(); B != E; ++B)
+  // HACK: this won't be needed when we'll migrate away from CommandLine.
+  std::stable_sort(Args.begin(), Args.end(), &CompareFirst<unsigned, std::string>);
+  for (ArgsVector::iterator B = Args.begin(), E = Args.end(); B != E; ++B) {
     Out.push_back(B->second);
+  }
 
   return Out;
 }