What I've got is a mess (I'm using Hubris OS, which seems to do everything in release mode)
```
[profile.release]
codegen-units = 1 # better optimizations
debug = 2 # symbols are nice and they don't increase the size on Flash
lto = true # better optimizations
opt-level = 3

[profile.release.package."*"]
debug=2

[profile.release.overrides."*"]
debug=2

[profile.dev.package."*"]
debug=2

[profile.dev.overrides."*"]
debug=2

[profile.dev]
opt-level = 1 # no optimizations was just too painful in terms of flash size
```