Fix Gepetto/aig#66

In short, we need `find_package(jrl-cmakemodules CONFIG REQUIRED)` to
work before `project(…)` call, because we want that `project(…)` to use our
`PROJECT_ARGS` from `jrl-cmakemodules`'s `compute_project_args()`.

But as long as `project(…)` with the correct `LANGUAGES` is not run (nor
is `enable_language(…)`), `CMAKE_LIBRARY_ARCHITECTURE` is not set,
and therefore, the "Config Mode Search Procedure"
https://cmake.org/cmake/help/latest/command/find_package.html#config-mode-search-procedure
will not include any `lib/<arch>` paths.

And by default, ROS packages all have `Architecture: any` in their
`debian/control`, which configure the installation of CMake export in
`lib/<arch>`:
https://github.com/ros2-gbp/jrl_cmakemodules-release/blob/debian/ros-humble-jrl-cmakemodules_1.1.0-1_jammy/debian/control#L10

By exporting this `architecture_independent` tag, we should be able to
get `Architecture: all`, and see this package correctly installed in
`lib`

Unfortunately, ros-infrastructure/bloom#705 is
not merged yet.

Fortunately, our lord and savior Nix can easily deal with that not-merged status:
lopsided98/nix-ros-overlay#736

Thanks @MaximilienNaveau for the report and the private follow-ups when
I could not understand or reproduce the issue.

Btw, calling `enable_language(…)` first, then
`find_package(jrl-cmakemodules …)`, and finally `project(…)` is a
working workaround, but CMP0165 decided to strictly forbid this in CMake >= 3.30.