message: wasmer-cli: refuse to build if not at least one compiler is enabled
diff: use wasmer_cli::cli::wasmer_main;
  +#[cfg(not(any(feature = "cranelift", feature = "singlepass", feature = "llvm")))]
  +compile_error!(
  + "Either enable at least one compiler, or compile the wasmer-headless binary instead"
  +);
  +
  fn main() {
  wasmer_main();
  }
  