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

tools/gn/command_analyze.cc

Index: tools/gn/command_analyze.cc
diff --git a/tools/gn/command_analyze.cc b/tools/gn/command_analyze.cc
index 6fd582356097f55d8f3326fe36c977b25a565422..c2b38835da0b8512ba335612e0db4b88281d31a3 100644
--- a/tools/gn/command_analyze.cc
+++ b/tools/gn/command_analyze.cc
@@ -110,10 +110,9 @@ int RunAnalyze(const std::vector<std::string>& args) {
   if (!setup->DoSetup(args[0], false) || !setup->Run())
     return 1;
 
-  Analyzer analyzer(setup->builder());
-
   Err err;
-  std::string output = Analyzer(setup->builder()).Analyze(input, &err);
+  Analyzer analyzer(setup->build_settings(), setup->builder());
+  std::string output = analyzer.Analyze(input, &err);
   if (err.has_error()) {
     err.PrintToStdout();
     return 1;