Dude lots of things wrong with that code.I'm posting the updated code this works.I have added comments so you figure it out.
Code:
#include<stdio.h>

void squeez(char *,char *,int ); 

int main()
{

    char s[] = "some text l";
    char z[] = "some text here";
    int l=sizeof(s);    
    squeez(s,z,l);    //call to function
    return(0);
}

void squeez(char *s,char *z,int l)
{
    char *k=z;
        int dummy = 0;
    
    int j=0;
        char x[l];
    
   while(*s !='\0')        /* the starting loop */
    {
        dummy=0;
    k=z;
        while(*k != '\0') /* inner loop */
        {
/* the purpose of dummy is to tell weather this if statement became true or not */
      
          if(*s==*k)
            {

                dummy = 1;    
        
               
            }    //end of if
                
            k++; //increment  pointer
        }        //exit inner loop
        if(dummy ==0)
            {
                x[j] = *s;
        j++;
            }
    s++;
    }  //exit outer loop
    
    puts(x); /* printing out the values */
}  //exit