Fix typo.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@54774 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/Driver/RewriteMacros.cpp b/Driver/RewriteMacros.cpp
index c298943..5500186 100644
--- a/Driver/RewriteMacros.cpp
+++ b/Driver/RewriteMacros.cpp
@@ -107,7 +107,7 @@
   
   // Preprocess the input file in parallel with raw lexing the main file. Ignore
   // all tokens that are preprocessed from a file other than the main file (e.g.
-  // a header).  If we see tokens that are in the preprocessed file bug not the
+  // a header).  If we see tokens that are in the preprocessed file but not the
   // lexed file, we have a macro expansion.  If we see tokens in the lexed file
   // that aren't in the preprocessed view, we have macros that expand to no
   // tokens, or macro arguments etc.