Produce proper exit status in case image has been built with timeout (a…

…pache#35282)

When we build the image with timeout, we fork the process and set alarm
and create a new process group in order to be sure that all the parallel
build processes can be killed easily with sending termination signal to
process group on timeout. In order to wait for the forked process
to complete we used waitpid, but we did not handle the status code
properly, so if the build failed, we returned with 0 exit code.

This had the side effect that "Build CI image" did not fail, instead
the next step (generating source providers failed instead and it was
not obvious that the CI image build failing was the root cause.

This PR properly retrieves the wait status and converts it to
exit code - since we are still supporting Python 3.8 this is still
done using a bit nasty set of if statements - only in Python 3.9 we
have `os.waitstatus_to_exitcode` method to do it for us, but we cannot
use the method yet.

dev/breeze/src/airflow_breeze/commands/ci_image_commands.py

@@ -206,6 +206,20 @@ def kill_process_group(build_process_group_id: int):
         pass
 
 
+def get_exitcode(status: int) -> int:
+    # In Python 3.9+ we will be able to use
+    # os.waitstatus_to_exitcode(status) - see https://github.com/python/cpython/issues/84275
+    # but until then we need to do this ugly conversion
+    if os.WIFSIGNALED(status):
+        return -os.WTERMSIG(status)
+    elif os.WIFEXITED(status):
+        return os.WEXITSTATUS(status)
+    elif os.WIFSTOPPED(status):
+        return -os.WSTOPSIG(status)
+    else:
+        return 1
+
+
 @ci_image.command(name="build")
 @option_python
 @option_run_in_parallel
@@ -277,8 +291,13 @@ def run_build(ci_image_params: BuildCiParams) -> None:
             atexit.register(kill_process_group, pid)
             signal.signal(signal.SIGALRM, handler)
             signal.alarm(build_timeout_minutes * 60)
-            os.waitpid(pid, 0)
-            return
+            child_pid, status = os.waitpid(pid, 0)
+            exit_code = get_exitcode(status)
+            if exit_code:
+                get_console().print(f"[error]Exiting with exit code {exit_code}")
+            else:
+                get_console().print(f"[success]Exiting with exit code {exit_code}")
+            sys.exit(exit_code)
         else:
             # turn us into a process group leader
             os.setpgid(0, 0)