Fix wasm build (#102)

* Reserve pages for heap at initialization time

Since it is freshly allocated memory it won't collide with stack, data or whatever else.

* Compile all wasm files with LTO.

Modules compiled without LTO contain undesired imports and outright invalid (e.g. type mismatches inside the wasm).

substrate/demo/runtime/wasm/Cargo.toml

@@ -28,6 +28,7 @@ std = [
 
 [profile.release]
 panic = "abort"
+lto = true
 
 [workspace]
 members = []