style: modernize to splitseq, cut, min, maps.copy and range-over-int

asm/riscv_goobj_test.go

@@ -141,7 +141,7 @@ DATA answer<>+0(SB)/8, $42
 	first := int(le.Uint32(relocIdx[4*(4+4):]))
 	wantType := []uint16{relocRISCVPcrelItype, relocRISCVPcrelItype, relocRISCVPcrelStype}
 	wantOffAbs := []int{0, 8, 16}
-	for i := 0; i < 3; i++ {
+	for i := range 3 {
 		e := relocs[(first+i)*23:]
 		if int32(le.Uint32(e[0:])) != int32(wantOffAbs[i]) || e[4] != 8 || le.Uint16(e[5:]) != wantType[i] ||
 			le.Uint32(e[15:]) != pkgIdxSelf || le.Uint32(e[19:]) != 0 {
@@ -221,7 +221,7 @@ func main() {
 		t.Fatalf("baseline build: %v\n%s", err, buildLog)
 	}
 	var pkgArch, work, linkLine, asmObj string
-	for _, line := range strings.Split(string(buildLog), "\n") {
+	for line := range strings.SplitSeq(string(buildLog), "\n") {
 		switch {
 		case strings.HasPrefix(line, "WORK="):
 			work = strings.TrimPrefix(line, "WORK=")
@@ -279,7 +279,7 @@ func main() {
 	newArch := filepath.Join(dir, "pkg.a")
 	args := []string{"tool", "pack", "c", newArch}
 	seen := map[string]bool{}
-	for _, m := range strings.Fields(string(listOut)) {
+	for m := range strings.FieldsSeq(string(listOut)) {
 		if seen[m] {
 			continue
 		}