Make debug builds more usable (#4683)

* Make debug builds more usable

This pr makes debug builds more usable in terms of `cargo run -- --dev`.

1. `--dev` activates `--execution native`, iff `--execution` is not
given or no sub `--execution-*` is given.
2. It was probably a mistake to compile WASM in debug for a debug build.
So, we now build the WASM binary always as `release` (if not requested
differently by the user). So, we trade compilation time for a better
debug experience.

* Make sure we only overwrite default values

* Make it work

* Apply suggestion

substrate/bin/node-template/runtime/build.rs

@@ -19,7 +19,7 @@ use wasm_builder_runner::{build_current_project_with_rustflags, WasmBuilderSourc
 fn main() {
 	build_current_project_with_rustflags(
 		"wasm_binary.rs",
-		WasmBuilderSource::Crates("1.0.8"),
+		WasmBuilderSource::Crates("1.0.9"),
 		// This instructs LLD to export __heap_base as a global variable, which is used by the
 		// external memory allocator.
 		"-Clink-arg=--export=__heap_base",