cmake: don't install config.h

This header is private and shouldn't be used by clients.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@149496 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 25be7e1..2087c6a 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -223,6 +223,7 @@
   FILES_MATCHING
   PATTERN "*.def"
   PATTERN "*.h"
+  PATTERN "config.h" EXCLUDE
   PATTERN ".svn" EXCLUDE
   )