Add host target platform (#4783)

Co-authored-by: Otto winter <otto@otto-winter.com>

esphome/components/host/__init__.py

@@ -0,0 +1,38 @@
+from esphome.const import (
+    KEY_CORE,
+    KEY_FRAMEWORK_VERSION,
+    KEY_TARGET_FRAMEWORK,
+    KEY_TARGET_PLATFORM,
+)
+from esphome.core import CORE
+import esphome.config_validation as cv
+import esphome.codegen as cg
+
+from .const import KEY_HOST
+
+# force import gpio to register pin schema
+from .gpio import host_pin_to_code  # noqa
+
+
+CODEOWNERS = ["@esphome/core"]
+AUTO_LOAD = ["network"]
+
+
+def set_core_data(config):
+    CORE.data[KEY_HOST] = {}
+    CORE.data[KEY_CORE][KEY_TARGET_PLATFORM] = "host"
+    CORE.data[KEY_CORE][KEY_TARGET_FRAMEWORK] = "host"
+    CORE.data[KEY_CORE][KEY_FRAMEWORK_VERSION] = cv.Version(1, 0, 0)
+    return config
+
+
+CONFIG_SCHEMA = cv.All(
+    cv.Schema({}),
+    set_core_data,
+)
+
+
+async def to_code(config):
+    cg.add_build_flag("-DUSE_HOST")
+    cg.add_define("ESPHOME_BOARD", "host")
+    cg.add_platformio_option("platform", "platformio/native")