erlang: normalize version name

All BEAM-related expressions are available via the top-level `beam` attribute, which includes:

- `interpreters`: a set of compilers running on the BEAM, including multiple Erlang/OTP versions (`beam.interpreters.erlangR22`, etc), Elixir (`beam.interpreters.elixir`) and LFE (Lisp Flavoured Erlang) (`beam.interpreters.lfe`).

- `interpreters`: a set of compilers running on the BEAM, including multiple Erlang/OTP versions (`beam.interpreters.erlang_22`, etc), Elixir (`beam.interpreters.elixir`) and LFE (Lisp Flavoured Erlang) (`beam.interpreters.lfe`).

- `packages`: a set of package builders (Mix and rebar3), each compiled with a specific Erlang/OTP version, e.g. `beam.packages.erlang22`.

To create a package builder built with a custom Erlang version, use the lambda, `beam.packagesWith`, which accepts an Erlang/OTP derivation and produces a package builder similar to `beam.packages.erlang`.

Many Erlang/OTP distributions available in `beam.interpreters` have versions with ODBC and/or Java enabled or without wx (no observer support). For example, there's `beam.interpreters.erlangR22_odbc_javac`, which corresponds to `beam.interpreters.erlangR22` and `beam.interpreters.erlangR22_nox`, which corresponds to `beam.interpreters.erlangR22`.

Many Erlang/OTP distributions available in `beam.interpreters` have versions with ODBC and/or Java enabled or without wx (no observer support). For example, there's `beam.interpreters.erlang_22_odbc_javac`, which corresponds to `beam.interpreters.erlang_22` and `beam.interpreters.erlang_22_nox`, which corresponds to `beam.interpreters.erlang_22`.

## Build Tools {#build-tools}

with import <nixpkgs> { };

let

  # beam.interpreters.erlangR23 is available if you need a particular version

  # beam.interpreters.erlang_23 is available if you need a particular version

  packages = beam.packagesWith beam.interpreters.erlang;

  pname = "your_project";

with pkgs;

let

  elixir = beam.packages.erlangR24.elixir_1_12;

  elixir = beam.packages.erlang_24.elixir_1_12;

in

mkShell {

  buildInputs = [ elixir ];