Fixes a crash when generating dependency file stuff

and output file is not writable. // rdar://9286457.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@129587 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Frontend/DependencyFile.cpp

@@ -171,7 +171,7 @@ void DependencyFileCallback::OutputDependencyFile() {
   *OS << '\n';
 
   // Create phony targets if requested.
-  if (PhonyTarget) {
+  if (PhonyTarget && !Files.empty()) {
     // Skip the first entry, this is always the input file itself.
     for (std::vector<std::string>::iterator I = Files.begin() + 1,
            E = Files.end(); I != E; ++I) {

test/Frontend/dependency-generation-crash.c

@@ -0,0 +1,4 @@
+// RUN: touch %t
+// RUN: chmod 0 %t
+// %clang -E -dependency-file bla -MT %t -MP -o %t -x c /dev/null
+// rdar://9286457