Remove unmaintained cross feature

This documentation is not maintained and it required to be moved inside
a separate project. We remove it and keep it out from the plain project
for now.

.gitignore

@@ -2,7 +2,3 @@ ltx
 libltx.so
 transport.in
 .venv
-zig-cache
-zig-out
-cross/initrds
-cross/kernels

README.md

@@ -28,9 +28,7 @@ LTX itself just needs Clang or GCC. The tests require Python 3.7+ with
 ## Build
 
 LTX can also be built as library in order to link its API inside a project and
-to run a custom initialization process for specific systems. This is currently
-used to [cross-compile kernel](/docs/cross.md) and to execute `ltx` as init
-process.
+to run a custom initialization process for specific systems, such as `initrd`.
 
     # libltx build
     make shared
@@ -55,9 +53,6 @@ For testing:
     # execute LTX communication tests
     pytest -v tests/test_ltx.py
 
-We can also [easily cross-compile LTX](/docs/cross.md) using `zig >=
-0.11.0`. Beware that this is an **experimental feature**.
-
 ## Run inside container
 
 We provide a `Dockerfile` that can be used to run LTX inside a container.