feat: add a compilation test to make sure the macros work

Author: fogti

examples/macros.rs

@@ -0,0 +1,10 @@
+//! This file tests if the macros defined by the hermit-entry crate,
+//! which affect linker .note entries, can actually be used.
+
+#[cfg(feature = "kernel")]
+hermit_entry::define_abi_tag!();
+
+#[cfg(feature = "kernel")]
+hermit_entry::define_entry_version!();
+
+fn main() {}