Document dependencies for the "spicy" targets

Author: rexim

README.md

@@ -13,13 +13,6 @@
 
 Compiler for the [B Programming Language](https://en.wikipedia.org/wiki/B_(programming_language)) implemented in [Crust](https://github.com/tsoding/crust).
 
-## Dependencies
-
-- [Rust](https://www.rust-lang.org/) - the compiler is written in it;
-- [GCC](https://gcc.gnu.org/) or [Clang](https://clang.llvm.org/) (whatever serves as the `cc` on your POSIX platform) - the `x86_64` and `aarch64` targets generate assembly and pass it to `cc` to assemble and link.
-
-<!-- TODO: document specific dependencies for the rest of the targets. Like mingw32-w64 and wine on Linux for gas-x86_64-Windows, etc. -->
-
 ## Quick Start
 
 ```console
@@ -30,6 +23,49 @@ $ ./build/b -run ./examples/hello_world.b
 Also check out more examples at [./examples/](./examples/).
 Find the project documentation at [./docs/](./docs/).
 
+## Dependencies
+
+Generally, to write programs for the three major contemporary platforms (Linux, Windows, Darwin) you need only these things:
+
+- [Rust](https://www.rust-lang.org/) - the compiler is written in it;
+- [GCC](https://gcc.gnu.org/) or [Clang](https://clang.llvm.org/) or [mingw-w64](https://www.mingw-w64.org/) (whatever serves as the `cc` on your POSIX platform) - the `x86_64` and `aarch64` targets generate assembly and pass it to `cc` to assemble and link.
+
+If you feel like playing with our "spicy" targets, you will need to setup few additional things.
+
+### uxn
+
+[Uxn](https://100r.co/site/uxn.html) is a pretty cool small virtual machine designed to be simple and portable.
+
+This compiler toolchain expects the `uxnemu` and `uxncli` executables to be available in the `$PATH` environment variable. We recommend to build them from the source code available at [https://git.sr.ht/~rabbits/uxn](https://git.sr.ht/~rabbits/uxn). Follow their build instructions and then copy the contents of the `bin/` folder somewhere were the `$PATH` points at.
+
+### 6502-posix
+
+[MOS Technology 6502](https://en.wikipedia.org/wiki/MOS_Technology_6502) is a legendary processor that was used in such systems as the Atari 2600, Atari 8-bit computers, Apple II, Nintendo Entertainment System, Commodore 64, Atari Lynx, BBC Micro and others.
+
+Since "targeting 6502" doesn't really mean anything, given the diverse array of hardware, we created a special target called [posix6502](https://github.com/bext-lang/posix6502). It's a simple 6502 emulator that exposes some POSIX functionality to programs running on the 6502 processor, allowing them to operate in a POSIX environment. We use it as a testing and playground target for 6502 codegen. In the future, we may add more 6502-related targets.
+
+It consist of a single `posix6502` executable which is expected to be available to the compiler toolchain via the `$PATH` environment variable. We recommend to build it from the source code:
+
+```console
+$ git clone https://github.com/bext-lang/posix6502 && cd posix6502
+$ cc -o nob nob.c
+$ ./nob
+```
+
+Copy the `build/posix6502` executable somewhere were the `$PATH` points at.
+
+### ilasm-mono
+
+This target tries to produce [.NET](https://dotnet.microsoft.com/en-us/)/[Mono](https://www.mono-project.com/) compatible binaries. It's currently a work-in-progress and does not have anything useful implemented in it.
+
+The compiler toolchain expects `ilasm` and `mono` executables available in the `$PATH` environment variables. Lots of Linux distros make them available via the mono packages in their official repos:
+
+```consols
+$ sudo xbps-install mono      # Void Linux
+$ sudo apt install mono-devel # Ubuntu
+...
+```
+
 ## Contribution
 
 Accepting Pull Requests is currently paused. We are in the middle of [Decentralizing](https://github.com/tsoding/b/issues/62) this repo. The plan is
@@ -38,7 +74,7 @@ Accepting Pull Requests is currently paused. We are in the middle of [Decentrali
 2. Keep `*x86_64*` and `*aarch64*` codegens in the main repo.
 3. Move codegens [6502](./src/codegen/mos6502.rs) (owner [@Miezekatze64](https://github.com/miezekatze64)), [uxn](./src/codegen/uxn.rs) (owner [@deniska](https://github.com/deniska)), [gas-sh4dsp-prizm](https://github.com/tsoding/b/pull/175) (owner [@seija-amanojaku](https://github.com/seija-amanojaku)) to separate repos within the organization and give the owners full admin access to them.
 
-You can still submit PRs in the meantime. Just don't expect them to be reviewed any time soon since decouping codegens requires extensive refactoring. They will be addressed eventually.
+You can still submit PRs in the meantime. Just don't expect them to be reviewed any time soon since decoupling codegens requires extensive refactoring. The PRs will be addressed eventually.
 
 ## References