[Bash-autocompletion] Fixed typo and add '-' after -Wno

Summary: -Wno-<warning> was autocompleted as -Wno<warning>, so fixed this typo.

Differential Revision: https://reviews.llvm.org/D35762

llvm-svn: 308824
diff --git a/clang/lib/Basic/DiagnosticIDs.cpp b/clang/lib/Basic/DiagnosticIDs.cpp
index 932b3f1..0cdaf8e 100644
--- a/clang/lib/Basic/DiagnosticIDs.cpp
+++ b/clang/lib/Basic/DiagnosticIDs.cpp
@@ -516,7 +516,7 @@
     std::string Diag(DiagGroupNames + I + 1, DiagGroupNames[I]);
     I += DiagGroupNames[I] + 1;
     Res.push_back("-W" + Diag);
-    Res.push_back("-Wno" + Diag);
+    Res.push_back("-Wno-" + Diag);
   }
 
   return Res;