The AArch64 ELF spec includes "mapping symbols" for identifying contiguous
data/code regions in a binary:
https://github.com/ARM-software/abi-aa/blob/main/aaelf64/aaelf64.rst#mapping-symbols

Ignore these if we encounter them in the ".defmt" section rather than returning
an error.

Error was:
```
error: &-masking with zero
  --> qemu/src/bin/bitflags.rs:10:1
   |
10 | / bitflags! {
11 | |     #[allow(clippy::bad_bit_mask)]
12 | |     struct Flags: u8 {
13 | |         #[cfg(not(never))]
...  |
23 | |     }
24 | | }
   | |_^
   |
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#bad_bit_mask
   = note: `#[deny(clippy::bad_bit_mask)]` on by default
   = note: this error originates in the macro `__impl_bitflags` which comes from the expansion of the macro `bitflags` (in Nightly builds, run with -Z macro-backtrace for more info)
```