Remove hardcoded refs from ociartifact code

Fixes: https://issues.redhat.com/browse/RUN-3578

Signed-off-by: Nicola Sella <nsella@redhat.com>

vendor/github.com/klauspost/compress/internal/snapref/decode.go

@@ -209,7 +209,7 @@ func (r *Reader) fill() error {
 			if !r.readFull(r.buf[:len(magicBody)], false) {
 				return r.err
 			}
-			for i := 0; i < len(magicBody); i++ {
+			for i := range len(magicBody) {
 				if r.buf[i] != magicBody[i] {
 					r.err = ErrCorrupt
 					return r.err

vendor/github.com/klauspost/compress/internal/snapref/encode.go

@@ -20,8 +20,10 @@ import (
 func Encode(dst, src []byte) []byte {
 	if n := MaxEncodedLen(len(src)); n < 0 {
 		panic(ErrTooLarge)
-	} else if len(dst) < n {
+	} else if cap(dst) < n {
 		dst = make([]byte, n)
+	} else {
+		dst = dst[:n]
 	}
 
 	// The block starts with the varint-encoded length of the decompressed bytes.