frame: GenesisBuild::build allowed in no_std (#14107)

* frame: GenesisBuild::build allowed in no_std

i`GenesisBuild::build` function will be required for no_std in no native
runtime world.

`GenesisBuild::build` macro generated function allows to build the runtime
GenesisConfig assembled from all pallets' GenesisConfigs.

* fixes

* GenesisBuild::build avaiable in no-std

- #[cfg(feature = "std")] is not longer added to GenesisBuild implementation.

* system: hash69 available for no-std

* elections-phragmen: panic message fixed for no_std

* frame::suport: doc updated

* test-runtime: default for GenesisConfig

* frame::test-pallet: serde/std added to std feature deps

* Cargo.toml: deps sorted

* Cargo.lock update

cargo update -p frame-support-test-pallet -p frame-support-test

* frame ui tests: cleanup

---------

Co-authored-by: parity-processbot <>

substrate/frame/support/src/traits/hooks.rs

@@ -361,13 +361,13 @@ pub trait Hooks<BlockNumber> {
 
 /// A trait to define the build function of a genesis config, T and I are placeholder for pallet
 /// trait and pallet instance.
-#[cfg(feature = "std")]
 pub trait GenesisBuild<T, I = ()>: Default + sp_runtime::traits::MaybeSerializeDeserialize {
 	/// The build function is called within an externalities allowing storage APIs.
 	/// Thus one can write to storage using regular pallet storages.
 	fn build(&self);
 
 	/// Build the storage using `build` inside default storage.
+	#[cfg(feature = "std")]
 	fn build_storage(&self) -> Result<sp_runtime::Storage, String> {
 		let mut storage = Default::default();
 		self.assimilate_storage(&mut storage)?;
@@ -375,6 +375,7 @@ pub trait GenesisBuild<T, I = ()>: Default + sp_runtime::traits::MaybeSerializeD
 	}
 
 	/// Assimilate the storage for this module into pre-existing overlays.
+	#[cfg(feature = "std")]
 	fn assimilate_storage(&self, storage: &mut sp_runtime::Storage) -> Result<(), String> {
 		sp_state_machine::BasicExternalities::execute_with_storage(storage, || {
 			self.build();