Reduce the number of worker threads GN uses.

tools/gn/target.cc

Index: tools/gn/target.cc
diff --git a/tools/gn/target.cc b/tools/gn/target.cc
index 36559823ee433dc7d826e9e48a95f85494b5ac02..4a93abc240cd36655d24a9ec8e0a9d52749e8543 100644
--- a/tools/gn/target.cc
+++ b/tools/gn/target.cc
@@ -12,6 +12,7 @@
 #include "tools/gn/filesystem_utils.h"
 #include "tools/gn/scheduler.h"
 #include "tools/gn/substitution_writer.h"
+#include "tools/gn/trace.h"
 
 namespace {
 
@@ -156,6 +157,9 @@ bool Target::OnResolved(Err* err) {
   DCHECK(output_type_ != UNKNOWN);
   DCHECK(toolchain_) << "Toolchain should have been set before resolving.";
 
+  ScopedTrace trace(TraceItem::TRACE_ON_RESOLVED, label());
+  trace.SetToolchain(settings()->toolchain_label());
+
   // Copy our own dependent configs to the list of configs applying to us.
   configs_.Append(all_dependent_configs_.begin(), all_dependent_configs_.end());
   MergePublicConfigsFrom(this, &configs_);