fix a bug #43984: tcc -run reports errno=2

The following program (errno.c) reports errno=2 when run
    using "tcc -run errno.c"

    #include <errno.h>
    #include <stdio.h>
    int main(void) { printf("errno=%d\n", errno); return 0; }

tccrun.c

@@ -127,6 +127,7 @@ LIBTCCAPI int tcc_run(TCCState *s1, int argc, char **argv)
         for (i=0; i<argc; ++i)
             bound_new_region(argv[i], strlen(argv[i]));
 
+	errno = 0; /* clean errno value */
         ret = (*prog_main)(argc, argv);
 
         /* unmark argv area */
@@ -137,7 +138,10 @@ LIBTCCAPI int tcc_run(TCCState *s1, int argc, char **argv)
         bound_exit();
     } else
 #endif
+    {
+	errno = 0; /* clean errno value */
         ret = (*prog_main)(argc, argv);
+    }
     return ret;
 }