[time] Skip automation.cpp when no on_time or on_time_sync automation is configured (#18750)

tests/component_tests/time/config/no_triggers.yaml

@@ -0,0 +1,15 @@
+esphome:
+  name: test
+
+esp32:
+  board: esp32dev
+  framework:
+    type: esp-idf
+
+wifi:
+  ssid: "test_ssid"
+  password: "test_password"
+
+time:
+  - platform: sntp
+    id: sntp_time

tests/component_tests/time/config/on_time.yaml

@@ -0,0 +1,21 @@
+esphome:
+  name: test
+
+esp32:
+  board: esp32dev
+  framework:
+    type: esp-idf
+
+wifi:
+  ssid: "test_ssid"
+  password: "test_password"
+
+logger:
+
+time:
+  - platform: sntp
+    id: sntp_time
+    on_time:
+      - seconds: 0
+        then:
+          - logger.log: tick

tests/component_tests/time/config/on_time_sync.yaml

@@ -0,0 +1,20 @@
+esphome:
+  name: test
+
+esp32:
+  board: esp32dev
+  framework:
+    type: esp-idf
+
+wifi:
+  ssid: "test_ssid"
+  password: "test_password"
+
+logger:
+
+time:
+  - platform: sntp
+    id: sntp_time
+    on_time_sync:
+      then:
+        - logger.log: synced

tests/component_tests/time/test_triggers.py

@@ -0,0 +1,28 @@
+"""automation.cpp (CronTrigger and SyncTrigger) is only compiled when an
+on_time or on_time_sync automation exists, so the define must follow them."""
+
+from collections.abc import Callable
+from pathlib import Path
+
+import pytest
+
+from esphome.core import CORE
+
+
+@pytest.mark.parametrize(
+    ("fixture", "emits"),
+    [
+        ("no_triggers.yaml", False),
+        ("on_time.yaml", True),
+        ("on_time_sync.yaml", True),
+    ],
+)
+def test_triggers_define_follows_automations(
+    fixture: str,
+    emits: bool,
+    generate_main: Callable[[str | Path], str],
+    component_config_path: Callable[[str], Path],
+) -> None:
+    generate_main(component_config_path(fixture))
+    defines = {define.name for define in CORE.defines}
+    assert ("USE_TIME_TRIGGERS" in defines) is emits