Clarify handling proc-macro panicking

[SOF3]

The RUSTFLAGS provided in the README does not work with proc-macro crates because compiling procedural macros requires the panic_unwind runtime. We would get this error instead:

error: the linked panic runtime `panic_unwind` is not compiled with this crate's panic strategy `abort`

It would be useful to document in the README what is suggested to be done in the case of workspaces with procedural macros. For example, are users advised to override the panic strategy through a certain cfg filter in Cargo.toml? Or are there other suggested tricks?

[MichaelScofield]

Running into the same problem here, any updates?