remedy for `eh_personality` error

[U007D]

If one happens to have a Cargo.toml profile set to unwinding panics, a language item required, but not found: 'eh_personality' error will result. PR #42 adds a brief note explaining how to resolve the error.

[gl4eqen]

It happened to me as well but it was caused by not setting a proper target

[build]
target = "thumbv7m-none-eabi"

in .cargo/config or via command-line options.

[tomioe]

[build]
target = "thumbv7m-none-eabi"

It should be:

[build]
target = "thumbv7em-none-eabihf"