feat: implement baremetal GC

fix: pthread gc

fix: xiao-esp32c3 symbol

refactor: use clite memset instead of linking

fix: stack top symbol

runtime/internal/lib/runtime/runtime_gc.go

@@ -1,4 +1,4 @@
-//go:build !nogc
+//go:build !nogc && !baremetal
 
 package runtime
 

runtime/internal/lib/runtime/runtime_gc_baremetal.go

@@ -0,0 +1,9 @@
+//go:build !nogc && baremetal
+
+package runtime
+
+import "github.com/goplus/llgo/runtime/internal/runtime/tinygogc"
+
+func GC() {
+	tinygogc.GC()
+}