Add dependency on libm as required by #93

Jan Breuer

2017-08-16 4f960d20c76cb67e206a62f0e6c7608d75693ddc

 examples/test-interactive/main.c

@@ -96,7 +96,7 @@
            scpi_input_buffer, SCPI_INPUT_BUFFER_LENGTH,
            scpi_error_queue_data, SCPI_ERROR_QUEUE_SIZE);

    //printf("%.*s %s\r\n",  3, "asdadasdasdasdas", "b");
    /* printf("%.*s %s\r\n",  3, "asdadasdasdasdas", "b"); */
    printf("SCPI Interactive demo\r\n");
    char smbuffer[10];
    while (1) {