Discard $XDG_CACHE_HOME in favor of $XDG_DATA_HOME, as some distro guidelines
erroneously propose to mount the cache on tmpfs.

* Report the name of an unreadable directory.

  * src/alire/alire-index_on_disk.adb (New_Handler.Process_Local_Index):
      If the Path isn't a readable directory (e.g. because it doesn't
      exist), add it to the message in Outcome_Failure.
  * testsuite/tests/index/local-index-not-found/test.py: updated for
      new 'not a readable directory' report format.

* Handle Windows separator doubling.

Document --chdir in user-changes

* Allow solving with unistalled tools as fallback

* Fix precedence of installed compiler over remote ones

* Add warning in solution diff about toolchain download

* Fallback on installed compiler over uninstalled one

This is after checking that the preferred compiler cannot fulfill the compiler
dependency.

* Tweaks to restore former behaviors

* Fix test that inadvertently used virtual crate

It should have been real all along without alternatives

* Rebase tweaks

* Reword information message

* Move configuration loading earlier

Also make sure it's impossible to use configuration before the proper path is
set.

* New test

* Better encapsulation

* Windows fix

* New warning for externally selected gnat

* New test

* Do not report a virtual crate as inexistent

* Test to avoid future regression

-gnatyg is "check standard GNAT style rules, same as ydISux", but in
GCC 14 it will include a new switch, -gnatyz (check parentheses not
required by operator precedence rules) which will mean that use of
extra parens to clarify intent without deep knowledge of the rules
will trigger fatal warnings; for example in alire-conditional_trees.adb

   function Contains_ORs (This : Tree) return Boolean is
      ((not This.Is_Empty) and then This.Root.Contains_ORs);
       ^

Refer GCC Bugzilla PR 112446.

  * alire_common.gpr (Style_Check_Switches): Remove -gnatyg and replace
    by the pre-GCC 14 equivalent.

* Avoid unhandled exception in `alr publish --tar`

Fixes #1214

Also unify a couple of error messages

* Update test to check this fix

* Self-review

* Fix command not found in actions

* New test

* Fix "-h/--help" being catched after "--"

* Bump clic dependency

* Fix test on Windows

* Remove duplication in error message output

* Early detect bad license among choices

* Fix bad license

* Fix error deduplication

* New test for default licenses

* implement -C/--chdir flag

* use `alr` instead of Alire in help text.

* test --chdir flag

* clean up with-chdir test

See comments in issue #1481

According to https://no-color.org/

"Enable shared dependencies by default" was in there twice.

* Set shared dependencies as the default

* user-changes.md: Explain shared builds

We were attempting to enter a folder that not always will exist.

* Auto-refresh indexes after some time (default 24h)

* ask user on first autoupdate

* User changes

* Test behavior on network failure

* New `alr printenv --last-build`

This may be useful when no direct editing of manifests is convenient, as
otherwise `printenv` will always use the manifest's configuration.

* make new behavior the default with fallback

* CI fixes