Do dir changes in properly.

Record the root source dir at the beginning of the script
and use it when changing directories later.
Adjust the release test script to use gnat_linux dir

Change the release test script to use explicitly gnat_linux
directory to make the installation phase to work properly.
Update NEWS for 2.9
Remove hardcoded -static from ahven_tests.gpr

Fedora packages Ahven as a shared library, so
we should not explicitly use static linking
in the tests.

Patch from Björn Persson, thanks!
No need to with ancestor (Ahven) in Ahven.Framework.

Noticed by GNAT.
Update platforms for 2.9 in README.
Use gnat-12 in Sourcehut Debian builds.
Fix project website in alire config.
Oops, Debian 11 is bullseye, not buster
Update installation instructions for Debian
Ignore .map and TEST-*.xml files

Ignore all generated linker .map files from robot directory
and all TEST-*.xml files from xml directory.
Fix the test case assertion exception wording in the manual.

The report and the fix from Rod Kay, thanks!
Update versions in README for 2.9.

Fedora is now at version 35 and Debian at version 11.
Move basic.robot to tests directory.

Create new directory 'robot/tests' for all the Robot Framework tests
and move the existing tests there.

Then we can run the tests with command 'robot tests'.
Move robot test executables to bin dir.

Move the test executables generated for the Robot Framework
tests to the robot/test_sources/bin directory.
Mention Git mirrors in
Change gnat-8 to gnat-10 in debian/stable build setup.

Sourcehut updated their debian/stable to bullseye,
which has gnat-10 package instead of gnat-8.
Add .editorconfig file.

Ada files use 3 spaces, Makefile tabs,
unix style newlines.
Mention SPDX identifier addition in NEWS.txt.