Disable all dependency output options when using the Tooling library.

It isn't appropriate for a tool to be stomping over the dependency files,
especially if the actual build uses a compiler other than Clang or the tool
cannot find all the headers for some reason (which would cause the existing
dependency file to be deleted).

If a tool actually needs to care about dependency files we can think about
adding a mechanism for getting to this information.

Differential Revision: http://llvm-reviews.chandlerc.com/D2912

llvm-svn: 202669
diff --git a/clang/lib/Tooling/Tooling.cpp b/clang/lib/Tooling/Tooling.cpp
index a58854d..ee110e3 100644
--- a/clang/lib/Tooling/Tooling.cpp
+++ b/clang/lib/Tooling/Tooling.cpp
@@ -99,6 +99,7 @@
       *Diagnostics);
   Invocation->getFrontendOpts().DisableFree = false;
   Invocation->getCodeGenOpts().DisableFree = false;
+  Invocation->getDependencyOutputOpts() = DependencyOutputOptions();
   return Invocation;
 }