fix

Improve the Bazel build. Attempt to fix previous errors recorded while
trying to publish ftxui in the Bazel Central Registry:
- https://github.com/bazelbuild/bazel-central-registry/pull/4485
- https://buildkite.com/bazel/bcr-presubmit/builds/13601#01968b61-f5b2-4d16-94d0-c87a03a1a23b

Test against "recent" platforms
-------------------------------

Previously, I got the error:
```
gcc: error: unrecognized command line option '-std-c++20'; did you mean '-std-c++2a'?
```
This was due to using old distribution like ubuntu 2004. Test against
newer platforms only to avoid GCC version<-9.x.y

Downgrade gtest version.
------------------------

I suspect this caused the Bazel Central Registry error:
```
file:///workdir/modules/googletest/1.15.2/MODULE.bazel:68:20: name 'use_repo_rule' is not defined
```
I hoped using a lower version will fix the issue.

Tag gtest as dev_dependency
---------------------------

Presumably, this should avoid dependants to fetch it?

Enable --features-layering_check
--------------------------------

Aka clang `-Wprivate-header`. Fix the encountered errors.

Use clang in the CI
-------------------

The CI was defining clang/gcc in the matrix, but was not using it. Fix
the bug.

CHANGELOG.md

@@ -1,20 +1,9 @@
 Changelog
 =========
 
-6.1.9 (2025-05-07)
+Future release
 ------------
 
-### Build
-If all goes well (pending), ftxui should appear in the Bazel central repository.
-It can be imported into your project using the following lines:
-
-**MODULE.bazel**
-```bazel
-bazel_dep(name = "ftxui", version = "6.1.9")
-```
-
-Thanks @robinlinden and @kcc for the reviews.
-
 ### dom
 - Bugfix: Restore the `dbox` behavior from ftxui 5.0.0. To apply bgcolor
   blending between the two layers, a new `dboxBlend` will be added.
@@ -25,6 +14,13 @@ Thanks @robinlinden and @kcc for the reviews.
 ### Build
 - Feature: Support `bazel` build system. See #1032.
   Proposed by Kostya Serebryany @kcc
+  If all goes well (pending), it should appear in the Bazel central repository.
+  It can be imported into your project using the following lines:
+
+  **MODULE.bazel**
+  ```bazel
+  bazel_dep(name = "ftxui", version = "6.1.8")
+  ```
 
   **BUILD.bazel**
   ```bazel

CMakeLists.txt

@@ -2,7 +2,7 @@ cmake_minimum_required(VERSION 3.12)
 
 project(ftxui
   LANGUAGES CXX
-  VERSION 6.1.9
+  VERSION 6.1.8
   DESCRIPTION "C++ Functional Terminal User Interface."
 )
 

MODULE.bazel

@@ -1,7 +1,7 @@
 # FTXUI module.
 module(
     name = "ftxui",
-    version = "6.1.9",
+    version = "6.1.8",
     compatibility_level = 6,
 )
 

README.md

@@ -348,7 +348,6 @@ Feel free to add your projects here:
 - [terminal-rain](https://github.com/Oakamoore/terminal-rain)
 - [keywords](https://github.com/Oakamoore/keywords) ([Play web version :heart:](https://oakamoore.itch.io/keywords))
 - [FTB - tertminal file browser](https://github.com/Cyxuan0311/FTB)
-- [SHOOT!](https://github.com/ShingZhanho/ENGG1340-Project-25Spring)
 
 ### [cpp-best-practices/game_jam](https://github.com/cpp-best-practices/game_jam)
 
@@ -373,7 +372,7 @@ include(FetchContent)
 
 FetchContent_Declare(ftxui
   GIT_REPOSITORY https://github.com/ArthurSonzogni/ftxui
-  GIT_TAG v6.1.9
+  GIT_TAG v6.1.8
 )
 
 FetchContent_GetProperties(ftxui)