GN: Add notion of 'complete' static libraries, akin to GYP.

tools/gn/target.cc

Index: tools/gn/target.cc
diff --git a/tools/gn/target.cc b/tools/gn/target.cc
index 592cceac8b4958239350f36f93d976984015ec4c..cc4da95e3c06f75c7894d13fb70c077570e88416 100644
--- a/tools/gn/target.cc
+++ b/tools/gn/target.cc
@@ -73,6 +73,7 @@ Target::Target(const Settings* settings, const Label& label)
       output_type_(UNKNOWN),
       all_headers_public_(true),
       check_includes_(true),
+      complete_static_lib_(false),
       testonly_(false),
       hard_dep_(false),
       toolchain_(NULL) {
@@ -160,6 +161,11 @@ bool Target::IsLinkable() const {
   return output_type_ == STATIC_LIBRARY || output_type_ == SHARED_LIBRARY;
 }
 
+bool Target::IsFinal() const {
+  return output_type_ == EXECUTABLE || output_type_ == SHARED_LIBRARY ||
+         (output_type_ == STATIC_LIBRARY && complete_static_lib_);
+}
+
 std::string Target::GetComputedOutputName(bool include_prefix) const {
   DCHECK(toolchain_)
       << "Toolchain must be specified before getting the computed output name.";