Dump input filelists in the PrettyStackTrace

This may help us reproduce a failing build when all we have is a build
log, and will become much more important in batch mode when we
/really/ need to know what ended up in what batch.

For now, this doesn't include /output/ filelists, because David's
about to mess with that code anyway to make things better around
supplementary outputs in batch mode. There is one weirdness there,
though, which is that ArgsToFrontendInputsConverter peeks at the
outputs to see whether we're doing single-threaded or multi-threaded
WMO.

lib/Frontend/CompilerInvocation.cpp

@@ -81,9 +81,11 @@ SourceFileKind CompilerInvocation::getSourceFileKind() const {
   llvm_unreachable("Unhandled InputFileKind in switch.");
 }
 
-static bool ParseFrontendArgs(FrontendOptions &opts, ArgList &args,
-                              DiagnosticEngine &diags) {
-  return ArgsToFrontendOptionsConverter(diags, args, opts).convert();
+static bool ParseFrontendArgs(
+    FrontendOptions &opts, ArgList &args, DiagnosticEngine &diags,
+    SmallVectorImpl<std::unique_ptr<llvm::MemoryBuffer>> *buffers) {
+  ArgsToFrontendOptionsConverter converter(diags, args, opts);
+  return converter.convert(buffers);
 }
 
 static void diagnoseSwiftVersion(Optional<version::Version> &vers, Arg *verArg,
@@ -961,9 +963,12 @@ bool ParseMigratorArgs(MigratorOptions &Opts, llvm::Triple &Triple,
   return false;
 }
 
-bool CompilerInvocation::parseArgs(ArrayRef<const char *> Args,
-                                   DiagnosticEngine &Diags,
-                                   StringRef workingDirectory) {
+bool CompilerInvocation::parseArgs(
+    ArrayRef<const char *> Args,
+    DiagnosticEngine &Diags,
+    SmallVectorImpl<std::unique_ptr<llvm::MemoryBuffer>>
+        *ConfigurationFileBuffers,
+    StringRef workingDirectory) {
   using namespace options;
 
   if (Args.empty())
@@ -989,7 +994,8 @@ bool CompilerInvocation::parseArgs(ArrayRef<const char *> Args,
     return true;
   }
 
-  if (ParseFrontendArgs(FrontendOpts, ParsedArgs, Diags)) {
+  if (ParseFrontendArgs(FrontendOpts, ParsedArgs, Diags,
+                        ConfigurationFileBuffers)) {
     return true;
   }