fix: add gc dummy mutex

runtime/internal/lib/runtime/runtime2.go

@@ -4,8 +4,6 @@
 
 package runtime
 
-import "runtime"
-
 // Layout of in-memory per-function information prepared by linker
 // See https://golang.org/s/go12symtab.
 // Keep in sync with linker (../cmd/link/internal/ld/pcln.go:/pclntab)
@@ -30,10 +28,6 @@ func StopTrace() {
 	panic("todo: runtime.StopTrace")
 }
 
-func ReadMemStats(m *runtime.MemStats) {
-	panic("todo: runtime.ReadMemStats")
-}
-
 func SetMutexProfileFraction(rate int) int {
 	panic("todo: runtime.SetMutexProfileFraction")
 }