fix buildfile/reader to read last line (without NEWLINE)

internal/buildfile/reader.go

@@ -37,13 +37,22 @@ func NewReader(ctx *instruction.ExecutionContext, buildfile io.Reader) (*Reader,
 
 	// add each line as instruction
 	l, reader := 0, bufio.NewReader(buildfile)
+	eof := false
 	for {
+		if eof {
+			break
+		}
+
 		l++
 
 		// read line until end
 		line, err := reader.ReadString('\n')
 		if err == io.EOF {
+			if len(line) > 0 {
+				eof = true
+			} else {
 				break
+			}
 		} else if err != nil {
 			return nil, LineError{l, err}
 		}