Honor board_build.ldscript for the native flash linker script

Published configs override it to reserve a filesystem region or correct
a board's assumed flash size; the routed value replaces the BOARDS
default, and a path is rejected since the name resolves via -L.

tests/unit_tests/build_gen/test_arduino8266.py

@@ -1291,3 +1291,36 @@ def test_generate_ld_scripts_gcc_change_invalidates_stamp(tmp_path: Path) -> Non
     with patch.object(arduino8266.subprocess, "run", return_value=result) as mock_run:
         _run_generate_ld_scripts(paths)
     mock_run.assert_called_once()
+
+
+def test_defines_flags_honors_f_cpu_override() -> None:
+    """board_build.f_cpu (a published-config overclock knob) reaches the
+    compile line; the default stays 80 MHz."""
+    _set_flags()
+    config = _resolve_build_config(_flag_defines(set(), []))
+    board_build = ESP8266_BOARD_BUILD["nodemcuv2"]
+    defines = _defines_flags(config, "dout", "nodemcuv2", board_build["defines"])
+    assert "-DF_CPU=80000000L" in defines
+    CORE.platformio_options = {"board_build.f_cpu": "160000000L"}
+    defines = _defines_flags(config, "dout", "nodemcuv2", board_build["defines"])
+    assert "-DF_CPU=160000000L" in defines
+    # A repeated option accumulates as a list; the last value wins
+    CORE.platformio_options = {"board_build.f_cpu": ["80000000L", "160000000L"]}
+    defines = _defines_flags(config, "dout", "nodemcuv2", board_build["defines"])
+    assert "-DF_CPU=160000000L" in defines
+
+
+def test_flash_ld_name_honors_ldscript_override(tmp_path: Path) -> None:
+    """board_build.ldscript (filesystem reservation, corrected flash size)
+    replaces the board default; a path is rejected since the name resolves
+    via the -L search path."""
+    assert arduino8266._flash_ld_name("nodemcuv2") == "eagle.flash.4m.ld"
+    CORE.platformio_options = {"board_build.ldscript": "eagle.flash.4m2m.ld"}
+    assert arduino8266._flash_ld_name("nodemcuv2") == "eagle.flash.4m2m.ld"
+    paths = _make_framework(tmp_path)
+    _set_flags()
+    content = _write_ninja(paths)
+    assert "-T eagle.flash.4m2m.ld" in content
+    CORE.platformio_options = {"board_build.ldscript": "../evil.ld"}
+    with pytest.raises(EsphomeError, match="bare script name"):
+        arduino8266._flash_ld_name("nodemcuv2")

tests/unit_tests/core/test_config.py

@@ -1397,8 +1397,8 @@ def test_esphome_build_internals_are_yaml_only() -> None:
 async def test_add_platformio_options_native_arduino(
     caplog: pytest.LogCaptureFixture,
 ) -> None:
-    """The native ESP8266 Arduino toolchain warns about ignored options the
-    same way the native IDF toolchain does."""
+    """The native ESP8266 Arduino toolchain honors board_build.f_cpu (a
+    real-world overclock knob) and warns about the rest like native IDF."""
     CORE.toolchain = Toolchain.ARDUINO
     CORE.data[KEY_CORE] = {
         KEY_TARGET_PLATFORM: "esp8266",
@@ -1408,11 +1408,19 @@ async def test_add_platformio_options_native_arduino(
     await config._add_platformio_options(
         {
             "board_build.f_cpu": "160000000L",
+            "board_build.ldscript": "eagle.flash.4m2m.ld",
+            "board_build.filesystem": "littlefs",
             "upload_speed": "115200",
         }
     )
 
-    assert "esphome->platformio_options->board_build.f_cpu is ignored" in caplog.text
+    assert CORE.platformio_options["board_build.f_cpu"] == "160000000L"
+    assert CORE.platformio_options["board_build.ldscript"] == "eagle.flash.4m2m.ld"
+    assert "board_build.f_cpu is ignored" not in caplog.text
+    assert "board_build.ldscript is ignored" not in caplog.text
+    assert (
+        "esphome->platformio_options->board_build.filesystem is ignored" in caplog.text
+    )
     assert "'arduino' toolchain" in caplog.text
     assert "upload_speed" not in caplog.text