Make debug info work when using -save-temps.
 - This is pretty ugly, but the most obvious solution. Chime in if you
   have a nicer one.

 - The problem is that with -save-temps, clang-cc has no idea what the
   name of the original input file is. However, the user expects to be
   able to set breakpoints based on the input file name.

 - We support this by providing a new option -main-file-name (similar
   to -dumpbase used by gcc) which allows the driver to pass in the
   original file name.

 - <rdar://problem/6753383> building with clang using --save-temps
   gets the compile unit name from the .i file...


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@68595 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Driver/Tools.cpp b/lib/Driver/Tools.cpp
index eb9bbf2..4ae96c2 100644
--- a/lib/Driver/Tools.cpp
+++ b/lib/Driver/Tools.cpp
@@ -74,6 +74,11 @@
   // The make clang go fast button.
   CmdArgs.push_back("-disable-free");
 
+  // Set the main file name, so that debug info works even with
+  // -save-temps.
+  CmdArgs.push_back("-main-file-name");
+  CmdArgs.push_back(darwin::CC1::getBaseInputName(Args, Inputs));
+
   if (isa<AnalyzeJobAction>(JA)) {
     // Add default argument set.
     //