Merge pull request #2741 from pan-/conf_flush_at_exit

Add configuration for IO flushing during exit.

Author: sg-

hal/common/retarget.cpp

@@ -609,9 +609,11 @@ extern "C" void exit(int return_code) {
 #endif
 
 #if DEVICE_STDIO_MESSAGES
+#if MBED_CONF_CORE_STDIO_FLUSH_AT_EXIT
     fflush(stdout);
     fflush(stderr);
 #endif
+#endif
 
 #if DEVICE_SEMIHOST
     if (mbed_interface_connected()) {

mbed_lib.json

@@ -9,6 +9,11 @@
         "stdio-baud-rate": {
             "help": "Baud rate for stdio",
             "value": 9600
+        },
+
+        "stdio-flush-at-exit": {
+            "help": "Enable or disable the flush of standard I/O's at exit.",
+            "value": true
         }
     }
 }