End build when wasm-builder does not find a prerequisite (#3030)

* End build when `wasm-builder` does not find a prerequisite

Using `compile_error!` was a stupid idea by me, as rust would not
re-execute the build.rs.

* Increment the `wasm-builder` version

* Update core/utils/wasm-builder/src/lib.rs

Co-Authored-By: André Silva <andre.beat@gmail.com>

substrate/core/utils/wasm-builder/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "substrate-wasm-builder"
-version = "1.0.2"
+version = "1.0.3"
 authors = ["Parity Technologies <admin@parity.io>"]
 description = "Utility for building WASM binaries"
 edition = "2018"