fix: try to add a bounds.o only if __bounds_init not found

fix: try to add a bounds.o only if __bounds_init not found

    /usr/local/lib/tcc/i386/bcheck.o: error: '__bound_error_msg' defined twice
    #include <stdio.h>
    int main ()
    {
        #if 1
    	    int v[10];
            v[10] = 0;
            fprintf(stderr, "is bounds error catched?\n");
        #endif
        return 0;
    }
    // tcc -b test.c