Implement tracking of BUILD.gn files used to define target, toolchain or

tools/gn/config.cc

Index: tools/gn/config.cc
diff --git a/tools/gn/config.cc b/tools/gn/config.cc
index c06632449a4634b0c807f010f7e6ff23088f8279..d670c052d4af8d67a7f09885a66e770f0a714183 100644
--- a/tools/gn/config.cc
+++ b/tools/gn/config.cc
@@ -8,10 +8,10 @@
 #include "tools/gn/input_file_manager.h"
 #include "tools/gn/scheduler.h"
 
-Config::Config(const Settings* settings, const Label& label)
-    : Item(settings, label),
-      resolved_(false) {
-}
+Config::Config(const Settings* settings,
+               const Label& label,
+               const std::set<uint32_t>& source_files_hashes)
+    : Item(settings, label, source_files_hashes), resolved_(false) {}
 
 Config::~Config() {
 }