all: replace non-trivial uses of package ioutil with os (#24886)

Co-authored-by: Martin Holst Swende <martin@swende.se>

internal/build/util.go

@@ -24,7 +24,6 @@ import (
 	"go/parser"
 	"go/token"
 	"io"
-	"io/ioutil"
 	"log"
 	"os"
 	"os/exec"
@@ -177,7 +176,7 @@ func UploadSFTP(identityFile, host, dir string, files []string) error {
 // package paths.
 func FindMainPackages(dir string) []string {
 	var commands []string
-	cmds, err := ioutil.ReadDir(dir)
+	cmds, err := os.ReadDir(dir)
 	if err != nil {
 		log.Fatal(err)
 	}