Remove setvbuf(<handle>, NULL, _IOLBF, 0) calls for Win32

On Win32 the setvbuf function requires the last parameter to be size between 2 and INT_MAX bytes, so the calls always failed. Since the whole point of the calls is to set line-buffered mode for the file handle and that's not supported on Win32 anyway, conditionally remove them.
Signed-off-by: NFilip Navara <filip.navara@gmail.com>
Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>

exec.c

@@ -1491,7 +1491,8 @@ void cpu_set_log(int log_flags)
             static char logfile_buf[4096];
             setvbuf(logfile, logfile_buf, _IOLBF, sizeof(logfile_buf));
         }
-#else
+#elif !defined(_WIN32)
+        /* Win32 doesn't support line-buffering and requires size >= 2 */
         setvbuf(logfile, NULL, _IOLBF, 0);
 #endif
         log_append = 1;

vl.c

@@ -5755,7 +5755,10 @@ int main(int argc, char **argv, char **envp)
         exit(1);
     }
 
+#ifndef _WIN32
+    /* Win32 doesn't support line-buffering and requires size >= 2 */
     setvbuf(stdout, NULL, _IOLBF, 0);
+#endif
 
     init_timers();
     if (init_timer_alarm() < 0) {