docs: ci: update docs such that custom build scripts are called by build.py

Author: NeroBurner

docs/creating-new/test/ci.rst

@@ -125,22 +125,12 @@ Environment variables:
 
 * **TOOLCHAIN** - build matrix's **toolchain** parameter
 * **PROJECT_DIR** - **example** parameter
+* **SCRIPT** - full path to file defined by **script** parameter, called by ``build.py`` before build
 
-Default build script for all runners is ``.github/workflows/ci/build.py`` (bash script)
+Default build script for all runners is ``.github/workflows/ci/build.py`` (python script)
 
-.. literalinclude:: ../../../.github/workflows/ci/build.sh
-  :language: BASH
-
-Default build script for Windows runner - ``.github/workflows/ci/build.cmd`` (batch file) is similar.
-
-* installs `Polly <https://github.com/cpp-pm/polly>`__ and all necessary dependencies
-* defines default environment variables
-* runs ``jenkins.py`` script to :ref:`test building of a project <testing locally>`.
-
-.. warning::
-  If you don't need to alter Polly installation or predefined environment variables,
-  don't copy and modify default script. Instead call the default script from your custom script,
-  see example.
+.. literalinclude:: ../../../.github/workflows/ci/build.py
+  :language: PYTHON
 
 **Examples of override build scripts:**
 
@@ -155,22 +145,16 @@ for Ubuntu runner ``cmake/projects/<PACKAGE_NAME>/ci/build-ubuntu.sh``:
   pip install virtualenv
   sudo apt-get install libgl1-mesa-dev
 
-  bash .github/workflows/ci/build.sh
-
 for macOS ``cmake/projects/<PACKAGE_NAME>/ci/build-macos.sh``
 
 .. code-block:: bash
 
   export HUNTER_JOBS_NUMBER=1
   pip install virtualenv
 
-  bash .github/workflows/ci/build.sh
-
 for Windows ``cmake/projects/<PACKAGE_NAME>/ci/build.cmd``:
 
 .. code-block:: batch
 
     set HUNTER_JOBS_NUMBER=1
     pip install virtualenv
-
-    .github/workflows/ci/build.cmd