cctag: disabled alignment blocks libEigen alignment for reverse dependencies

[zeuner]

Describe the bug

cctag is currently compiled with libEigen alignment disabled, although it should be possible to enable in on modern compilers (see https://github.com/alicevision/CCTag/blob/develop/src/CMakeLists.txt#L250). When libEigen alignment are disabled in cctag, reverse dependencies that link to cctag also need to disable libEigen alignments in order to ensure binary compatibility.

Steps To Reproduce

Steps to reproduce the behavior:

1. build cctag
2. look into $dev/lib/cmake/CCTag/CCTagTargets.cmake
3. see these exported definitions: EIGEN_MAX_ALIGN_BYTES=0;EIGEN_MAX_STATIC_ALIGN_BYTES=0

Expected behavior

cctag does not export definitions that disable libEigen alignments (e.g. EIGEN_MAX_ALIGN_BYTES=0;EIGEN_MAX_STATIC_ALIGN_BYTES=0)

Additional context

With this being fixed, AliceVision could be compiled with libEigen alignments and cctag support here: #256115

Notify maintainers

@hesiod

Metadata

$ nix-shell -p nix-info --run "nix-info -m"
 - system: `"x86_64-linux"`
 - host os: `Linux 5.15.0-84-generic, Ubuntu, 22.04.3 LTS (Jammy Jellyfish), nobuild`
 - multi-user?: `yes`
 - sandbox: `no`
 - version: `nix-env (Nix) 2.6.0`
 - channels(root): `"nixpkgs"`
 - nixpkgs: `/root/.nix-defexpr/channels/nixpkgs`