crypto: fix ineffectual assignments (#22124)

* crypto/bls12381: fixed ineffectual assignment

* crypto/signify: fix ineffectual assignment

crypto/bls12381/arithmetic_fallback.go

@@ -207,7 +207,7 @@ func lsubAssign(z, x *fe) {
 	z[2], b = bits.Sub64(z[2], x[2], b)
 	z[3], b = bits.Sub64(z[3], x[3], b)
 	z[4], b = bits.Sub64(z[4], x[4], b)
-	z[5], b = bits.Sub64(z[5], x[5], b)
+	z[5], _ = bits.Sub64(z[5], x[5], b)
 }
 
 func neg(z *fe, x *fe) {

crypto/signify/signify_fuzz.go

@@ -25,7 +25,6 @@ import (
 	"log"
 	"os"
 	"os/exec"
-	"runtime"
 
 	fuzz "github.com/google/gofuzz"
 	"github.com/jedisct1/go-minisign"
@@ -129,6 +128,9 @@ func getKey(fileS string) (string, error) {
 func createKeyPair() (string, string) {
 	// Create key and put it in correct format
 	tmpKey, err := ioutil.TempFile("", "")
+	if err != nil {
+		panic(err)
+	}
 	defer os.Remove(tmpKey.Name())
 	defer os.Remove(tmpKey.Name() + ".pub")
 	defer os.Remove(tmpKey.Name() + ".sec")