Fix gcc warning about C++ style comments.

llvm-svn: 201512
diff --git a/clang/include/clang-c/BuildSystem.h b/clang/include/clang-c/BuildSystem.h
index 400ee6e..42a3e44 100644
--- a/clang/include/clang-c/BuildSystem.h
+++ b/clang/include/clang-c/BuildSystem.h
@@ -40,5 +40,5 @@
 }
 #endif
 
-#endif // CLANG_BUILD_SYSTEM_H
+#endif /* CLANG_BUILD_SYSTEM_H */