Refactor build scripts.

substrate/init.sh

@@ -0,0 +1,19 @@
+#!/bin/bash
+
+set -e
+
+echo "*** Initilising WASM build environment"
+
+rustup update nightly
+rustup target add wasm32-unknown-unknown --toolchain nightly
+rustup update stable
+
+# Install wasm-gc. It's useful for stripping slimming down wasm binaries.
+command -v wasm-gc || \
+	cargo +nightly install --git https://github.com/alexcrichton/wasm-gc
+
+# At the moment of writing, rustc still uses LLD 6 which produces wasm binaries
+# that don't export a table. Meanwhile, we are waiting for LLD 7 to come
+# in rustc we could use this handy little tool.
+command -v wasm-export-table || \
+	cargo +nightly install --git https://github.com/pepyakin/wasm-export-table.git