Don't inherit source sets across static libs in GN.

tools/gn/target.cc

Index: tools/gn/target.cc
diff --git a/tools/gn/target.cc b/tools/gn/target.cc
index 2ddbde91cf7fe964d76eb7a415bcdec7b7bed223..9bfae3593c32222bdd672ba382f9391701e0ac0b 100644
--- a/tools/gn/target.cc
+++ b/tools/gn/target.cc
@@ -177,8 +177,13 @@ void Target::PullDependentTargetInfo(std::set<const Config*>* unique_configs) {
         dep->output_type() != EXECUTABLE) {
       const std::set<const Target*> inherited = dep->inherited_libraries();
       for (std::set<const Target*>::const_iterator i = inherited.begin();
-           i != inherited.end(); ++i)
-        inherited_libraries_.insert(*i);
+           i != inherited.end(); ++i) {
+        // Don't copy source sets across static library boundaries. The static
+        // library will include all the files from the source set.
+        if (!(dep->output_type() == STATIC_LIBRARY &&
+              (*i)->output_type() == SOURCE_SET))
+          inherited_libraries_.insert(*i);
+      }
 
       // Inherited library settings.
       all_lib_dirs_.append(dep->all_lib_dirs());