Fix cmake build after recent JSON changes

I have moved StringExtractor.h into the include/ folder so that it can be properly included by
everyone.

llvm-svn: 241572
diff --git a/lldb/source/Utility/StringExtractor.cpp b/lldb/source/Utility/StringExtractor.cpp
index bde5e19..6302c03 100644
--- a/lldb/source/Utility/StringExtractor.cpp
+++ b/lldb/source/Utility/StringExtractor.cpp
@@ -7,7 +7,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "Utility/StringExtractor.h"
+#include "lldb/Utility/StringExtractor.h"
 
 // C Includes
 #include <stdlib.h>