Probably the easiest but worst way to detect lldb.

_.c

#include <string.h>
#include <stdio.h>
#include <stdlib.h>

int main()
{
    char *underscore = getenv("_");
    if (!strcmp(underscore, "/usr/bin/lldb"))
    {
        printf("lldb detected.\n");
    }
    else
    {
       printf("all good.\n");
    }
    
    return 0;
}