syz-repro: print detailed listings

Final reproducers are crafty. Sometimes they just stop working.
In that case the detailed listings of the programs executed by syz-repro
are very helpful. Let's print them at the loglevel 3.
diff --git a/pkg/repro/repro.go b/pkg/repro/repro.go
index 7aafdde..5db4116 100644
--- a/pkg/repro/repro.go
+++ b/pkg/repro/repro.go
@@ -548,6 +548,7 @@
 		ctx.cfg.TargetOS, ctx.cfg.TargetArch, opts.Sandbox, opts.Repeat,
 		opts.Threaded, opts.Collide, opts.Procs, -1, -1, vmProgFile)
 	ctx.reproLog(2, "testing program (duration=%v, %+v): %s", duration, opts, program)
+	ctx.reproLog(3, "detailed listing:\n%s", pstr)
 	return ctx.testImpl(inst.Instance, command, duration)
 }