Some examples produce warnings when run

[austinglaser]

The two I've seen are:

warning: trait objects without an explicit `dyn` are deprecated
 --> /home/austin/repos/personal/embedonomicon/ci/asm/rt/build.rs:5:29
  |
5 | fn main() -> Result<(), Box<Error>> {
  |                             ^^^^^ help: use `dyn`: `dyn Error`
  |
  = note: `#[warn(bare_trait_objects)]` on by default

and

warning: unused `core::result::Result` that must be used
  --> src/main.rs:22:5
   |
22 |     writeln!(hstdout, "{:#x}", &B as *const u8 as usize);
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = note: this `Result` may be an `Err` variant, which should be handled
   = note: this warning originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)

It should be relatively easy to fix these both