Add support for Vivado Core Container IP files (.xcix)

As mentioned in #68 (closed), a new release of Hog (v7.27.0) has been produced to add support for the .xcix files (Vivado Core Container IP files). This MR updates Hog to restore the GEM X2O flavors in GitLab CI.

Additionally, this commit should avoid stuck GitLab CI pipelines due to the (planned) removal of the docker runners from the CERN instance. The CI however remains broken due to the merge_and_tag job being stuck. Debugging is hard/impossible without access to the CI/CD settings. Similarly, the X2O flavors do not pass the CI due to problems in the boards/x2o/bd/blobfish/framework.bd file (i.e. [BD 41-758] The following clock pins are not connected to a valid clock source: /c2c_reset_fsm/phy_clk).

Also note the following changes made necessary by Hog behavior updates:

• Manually upgrade IP cores in order to re-target them to the part of the current build. This was previously done by the Hog framework.
• Systematically unset the Python environment variables when calling the Makefile script. The conditional method seemed broken with the updated Hog release.

Those two changes have been implemented via default hook scripts, which can themselves import project-specific code.

Fixes #68 (closed).

After merging this MR, all hacks related to the TCLink XCIX files in !145 should be removed.