Error: 'system' was not declared in this scope

$ cat main.c
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
 
#ifdef WIN32
  #include <fcntl.h>
  int pipe(int *files){return _pipe(files, 4096, O_BINARY);}
#endif
 
int call(char *cmd, FILE **fout, FILE **ferr){
  int outpipe[2], errpipe[2], bkp[2];
  int res;
  //создаем каналы
  if(pipe(outpipe)!= 0)goto call_err;
  if(pipe(errpipe)!= 0)goto call_err1;
  //бэкапим stdio
  bkp[0] = dup(fileno(stdout));
  bkp[1] = dup(fileno(stderr));
  if((bkp[0]==-1) || (bkp[1]==-1))goto call_err2;
  //отображаем созданные каналы на stdio
  if(dup2(outpipe[1], fileno(stdout))==-1)goto call_err2;
  if(dup2(errpipe[1], fileno(stderr))==-1)goto call_err2;
  
  res = system(cmd);
  
  //восстанавливаем stdio из бэкапа
  dup2(bkp[0], fileno(stdout));
  dup2(bkp[1], fileno(stderr));
  //преобразуем из идентификаторов в FILE
  *fout= fdopen(outpipe[0], "r");
  *ferr= fdopen(errpipe[0], "r");
  return res;
call_err2:
  dup2(bkp[1], fileno(stdout));
  dup2(bkp[2], fileno(stderr));
call_err1:
  close(errpipe[0]);
call_err:
  *fout=NULL; *ferr=NULL;
  return -1;
}
 
int main(){
  char str[100];
  FILE *fout, *ferr;
  
  call("dir", &fout, &ferr);
  
  fgets(str, 99, fout);
  printf("[%s]\n", str);
  
  fclose(fout);
  fclose(ferr);
}
 
$ gcc main.c -Wall -Wextra -Wpedantic -Os -gdwarf
main.c: In function ‘call’:
main.c:35:3: warning: ‘bkp[2]’ may be used uninitialized in this function [-Wmaybe-uninitialized]
   35 |   dup2(bkp[2], fileno(stderr));
      |   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
$ ./a.out 
[1.txt            lua.lua          wine32
]
 
$ i686-w64-mingw32-gcc main.c -Wall -Wextra -Wpedantic -Os -gdwarf 
main.c: In function ‘call’:
main.c:35:3: warning: array subscript 2 is above array bounds of ‘int[2]’ [-Warray-bounds]
   35 |   dup2(bkp[2], fileno(stderr));
      |   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
main.c:11:31: note: while referencing ‘bkp’
   11 |   int outpipe[2], errpipe[2], bkp[2];
      |                               ^~~
 
$ wine a.exe 
0016:err:ntoskrnl:ZwLoadDriver failed to create driver L"\\Registry\\Machine\\System\\CurrentControlSet\\Services\\NDIS": 00000001
0022:err:ntoskrnl:ZwLoadDriver failed to create driver L"\\Registry\\Machine\\System\\CurrentControlSet\\Services\\wineusb": c0000142
wine: Read access denied for device L"\\??\\Z:\\", FS volume label and serial are not available.
[Том на диске Z не имеет метки.
]