Xcode duplicate symbol '_main'

Question

I have a bunch of .O files that I generated from a makefile.u which compiles some .C files. I put all of the .O files into my Xcode project and I receive the below error when it builds:

duplicate symbol '_main' in:
     /Users/.../Objects-normal/arm64/AppDelegate.o
     /Users/.../LIBF2C/main.o
ld: 1 duplicate symbol for architecture arm64

I think I am bit confused because the main.o file is needed for my library, but the error seems to be telling me that I cannot have _main declared twice. So is there a solution for this, am I supposed to rename something to get it to build or any other ideas for how this can get resolved?

For some added context, this is specifically for the f2c libraries. So main.c(->main.o) from libf2c is:

/* STARTUP PROCEDURE FOR UNIX FORTRAN PROGRAMS */

#include "stdio.h"
#include "signal1.h"

#ifndef SIGIOT
#ifdef SIGABRT
#define SIGIOT SIGABRT
#endif
#endif

#ifndef KR_headers
#undef VOID
#include "stdlib.h"
#ifdef __cplusplus
extern "C" {
#endif
#endif

#ifndef VOID
#define VOID void
#endif

#ifdef __cplusplus
extern "C" {
#endif

#ifdef NO__STDC
#define ONEXIT onexit
extern VOID f_exit();
#else
#ifndef KR_headers
extern void f_exit(void);
#ifndef NO_ONEXIT
#define ONEXIT atexit
extern int atexit(void (*)(void));
#endif
#else
#ifndef NO_ONEXIT
#define ONEXIT onexit
extern VOID f_exit();
#endif
#endif
#endif

#ifdef KR_headers
extern VOID f_init(), sig_die();
extern int MAIN__();
#define Int /* int */
#else
extern void f_init(void), sig_die(const char*, int);
extern int MAIN__(void);
#define Int int
#endif

static VOID sigfdie(Sigarg)
{
Use_Sigarg;
sig_die("Floating Exception", 1);
}


static VOID sigidie(Sigarg)
{
Use_Sigarg;
sig_die("IOT Trap", 1);
}

#ifdef SIGQUIT
static VOID sigqdie(Sigarg)
{
Use_Sigarg;
sig_die("Quit signal", 1);
}
#endif


static VOID sigindie(Sigarg)
{
Use_Sigarg;
sig_die("Interrupt", 0);
}

static VOID sigtdie(Sigarg)
{
Use_Sigarg;
sig_die("Killed", 0);
}

#ifdef SIGTRAP
static VOID sigtrdie(Sigarg)
{
Use_Sigarg;
sig_die("Trace trap", 1);
}
#endif


int xargc;
char **xargv;

#ifdef __cplusplus
    }
#endif

 int
#ifdef KR_headers
main(argc, argv) int argc; char **argv;
#else
main(int argc, char **argv)
#endif
{
xargc = argc;
xargv = argv;
signal1(SIGFPE, sigfdie);   /* ignore underflow, enable overflow */
#ifdef SIGIOT
signal1(SIGIOT, sigidie);
#endif
#ifdef SIGTRAP
signal1(SIGTRAP, sigtrdie);
#endif
#ifdef SIGQUIT
if(signal1(SIGQUIT,sigqdie) == SIG_IGN)
    signal1(SIGQUIT, SIG_IGN);
#endif
if(signal1(SIGINT, sigindie) == SIG_IGN)
    signal1(SIGINT, SIG_IGN);
signal1(SIGTERM,sigtdie);

#ifdef pdp11
    ldfps(01200); /* detect overflow as an exception */
#endif

f_init();
#ifndef NO_ONEXIT
ONEXIT(f_exit);
#endif
MAIN__();
#ifdef NO_ONEXIT
f_exit();
#endif
exit(0);    /* exit(0) rather than return(0) to bypass Cray bug */
return 0;   /* For compilers that complain of missing return values; */
        /* others will complain that this is unreachable code. */
}
#ifdef __cplusplus
}
#endif