A readme/installation doc about deployment requirements.

[mmzx]

The Issue I had: Linking against lzma package under a freshly installed debian-10.3.0

lzma> Configuring lzma-0.0.0.3...
lzma> Cabal-simple_mPHDZzAJ_3.0.1.0_ghc-8.8.3: Missing dependency on a foreign
lzma> library:    
lzma> * Missing (or bad) header file: lzma.h
lzma> * Missing (or bad) C library: lzma
lzma> This problem can usually be solved by installing the system package that
lzma> provides this library (you may need the "-dev" version). If the library is
lzma> already installed but in a non-standard location then you can use the flags
lzma> --extra-include-dirs= and --extra-lib-dirs= to specify where it is.If the
lzma> library file does exist, it may contain errors that are caught by the C
lzma> compiler at the preprocessing stage. In this case you can re-run configure
lzma> with the verbosity flag -v3 to see the error messages.
lzma> If the header file does exist, it may contain errors that are caught by the C
lzma> compiler at the preprocessing stage. In this case you can re-run configure
lzma> with the verbosity flag -v3 to see the error messages.
lzma>

The solution:
apt install liblzma-dev

The proposal:

Personally I am inexperienced with debian like package management and it would have been nice to have a quick readme what I would have needed to do right away to be able to link the lzma package successfully.

This ticket is just a tiny bit of fragment now, but if there was enough content and a file to host such documentation I would be happy to help further.

[hvr]

Well, there's various distros, and it doesn't really scale for every FFI package to repeat the very same boilerplate in their README; hence why cabal is trying emit a generic message that applies more generally to this.

Maybe we should have a Wiki page the cabal message could link too, to go into more detail what

This problem can usually be solved by installing the system package that provides this library (you may need the "-dev" version)

entails for different Linux distros (and also non-Linux OS).

[georgefst]

apt install liblzma-dev

Thanks @mmzx! This just saved my when trying to build ghcup (which depends on this lib) on Ubuntu, where I thought installing apt install lzma-dev would be enough. In hindsight apt list *lzma* would have been a good idea, but it is easy to get stumped by this.

Anyway, I don't really have a suggestion - obviously it wouldn't be productive to list the subtleties for every possible distro...

[mmzx]

Having it amongst the issues is also not appropriate. Though, I am glad you have been able to find this!