Fix error reporting in the PNaCl bitcode reader.

tools/pnacl-abicheck/pnacl-abicheck.cpp

Index: tools/pnacl-abicheck/pnacl-abicheck.cpp
diff --git a/tools/pnacl-abicheck/pnacl-abicheck.cpp b/tools/pnacl-abicheck/pnacl-abicheck.cpp
index d5c9a76c5a6562a55cd10ee30e2f3b1a3f27a192..6ec63ff8f8c0e112f388dfc8d670cdb5d80cf00e 100644
--- a/tools/pnacl-abicheck/pnacl-abicheck.cpp
+++ b/tools/pnacl-abicheck/pnacl-abicheck.cpp
@@ -29,6 +29,12 @@ static cl::opt<std::string>
 InputFilename(cl::Positional, cl::desc("<input bitcode>"), cl::init("-"));
 
 static cl::opt<bool>
+VerboseErrors(
+    "verbose-parse-errors",
+    cl::desc("Print out more descriptive PNaCl bitcode parse errors"),
+    cl::init(false));
+
+static cl::opt<bool>
 Quiet("q", cl::desc("Do not print error messages"));
 
 static cl::opt<NaClFileFormat>
@@ -61,8 +67,12 @@ int main(int argc, char **argv) {
   SMDiagnostic Err;
   cl::ParseCommandLineOptions(argc, argv, "PNaCl Bitcode ABI checker\n");
 
+  if (Quiet)
+    VerboseErrors = false;
+
+  raw_ostream *Verbose = VerboseErrors ? &errs() : nullptr;
   std::unique_ptr<Module> Mod(
-      NaClParseIRFile(InputFilename, InputFileFormat, Err, Context));
+      NaClParseIRFile(InputFilename, InputFileFormat, Err, Verbose, Context));
   if (Mod.get() == 0) {
     Err.print(argv[0], errs());
     return 1;