move out c/cpp/py

cl/_testrt/fprintf/in.go

@@ -0,0 +1,16 @@
+package main
+
+import "unsafe"
+
+//go:linkname cstr llgo.cstr
+func cstr(string) *int8
+
+//go:linkname stderr __stderrp
+var stderr unsafe.Pointer
+
+//go:linkname fprintf C.fprintf
+func fprintf(fp unsafe.Pointer, format *int8, __llgo_va_list ...any)
+
+func main() {
+	fprintf(stderr, cstr("Hello %d\n"), 100)
+}