Fix sdkconfig(.defaults) changes not applying

Previously when changing sdkconfig or sdkconfig.defaults files
these changes were not applied without a `cargo clean`.

This is fixed by removing the generated `sdkconfig` file in the out
before the build of the esp-idf. Note though, that changing a
sdkconfig value will now recompile the whole esp-idf.

build/native.rs

@@ -255,6 +255,11 @@ fn build_cargo_first() -> Result<EspIdfBuildOutput> {
 
     env::set_var("PATH", &idf.exported_path);
 
+    // Remove the sdkconfig file generated by the esp-idf so that potential changes
+    // in the user provided sdkconfig and sdkconfig.defaults don't get ignored.
+    // Note: I'm really not sure why we have to do this.
+    let _ = fs::remove_file(path_buf![&out_dir, "sdkconfig"]);
+
     // Create cmake project.
     copy_file_if_different(
         manifest_dir.join(path_buf!("resources", "cmake_project", "CMakeLists.txt")),
@@ -378,7 +383,6 @@ fn build_cargo_first() -> Result<EspIdfBuildOutput> {
     )?;
 
     let mut cmake_config = cmake::Config::new(&out_dir);
-
     cmake_config
         .generator(cmake_generator.name())
         .out_dir(&out_dir)