Add a project setting to enable stdout flushing in release builds

[Calinou]

This can be used in server builds for journalctl compatibility.

This closes godotengine/godot-proposals#1912.

[akien-mga]

Thanks!

[akien-mga]

Cherry-picked for 3.2.4.

[akien-mga]

Cherry-picked for 3.2.4.

Reverted before 3.2.4 beta 5 due to #44850.

It's still merged in master which is still affected by #44850.

[Calinou]

Now that we've found a fix in master, can this be cherry-picked to 3.2 again with #45853 applied on top? Thanks in advance 🙂

[akien-mga]

Cherry-picked for 3.2.4. (Together with #45853 squashed in the cherry-pick.)

[PizzaConsole]

I am still getting this error on ubuntu 20.04

Godot Engine v3.2.4.rc3.mono.official - https://godotengine.org

ERROR: get_language_code: Condition "p_locale.length() < 2" is true. Returned: p_locale
   At: core/translation.cpp:945.
ERROR: set_locale: Unsupported locale 'C', falling back to 'en'.
   At: core/translation.cpp:969.

However, it does not exit my application service, so that fixes my core problem. it does give me this feedback-

server.service - My application service
     Loaded: loaded (/etc/systemd/system/server.service; enabled; vendor preset: enabled)
     Active: active (running) since Tue 2021-02-23 19:50:22 UTC; 46s ago
   Main PID: 1790 (godot-server)
      Tasks: 6 (limit: 2344)
     Memory: 32.1M
At: core/os/dir_access.cpp:185.
ERROR: get_language_code: Condition "p_locale.length() < 2" is true. Returned: p_locale
At: core/translation.cpp:945.
ERROR: set_locale: Unsupported locale 'C', falling back to 'en'.
At: core/translation.cpp:969.
ERROR: make_dir_recursive: Method failed. Returning: err
At: core/os/dir_access.cpp:185.
ERROR: _try_create_logs_dir: Condition "logs_mkdir_err != OK" is true. Returned: false
At: modules/mono/mono_gd/gd_mono_log.cpp:109.
Mono: No log file, using default log handler