Improve error output of wasm-builder when wasm ins't installed (#7105)

This improves the error message of wasm-builder when the wasm toolchain
isn't installed. Currently we print that the wasm toolchain is not
installed, but the actual problem is that there is a bug in the
packaging in rust. This will now be much easier to debug, by printing
the full error message of the compiler.

substrate/utils/wasm-builder/src/lib.rs

@@ -179,7 +179,7 @@ pub fn build_project_with_default_rustflags(
 			bloaty.wasm_binary_bloaty_path_escaped(),
 		)
 	};
-	
+
 	write_file_if_changed(
 			file_name.into(),
 			format!(
@@ -309,3 +309,8 @@ impl CargoCommand {
 				.contains("-nightly")
 	}
 }
+
+/// Returns `true` when color output is enabled.
+fn color_output_enabled() -> bool {
+	env::var(crate::WASM_BUILD_NO_COLOR).is_err()
+}