coreos-base/coreos-init: add EGIT_BRANCH

[tormath1]

As we are using the git eclass, we can't simply use a git ref if this one is on another branch, we need to pass the git branch as well.

---

Locally tested with:

$ ebuild coreos-init-0.0.1-r196.ebuild clean prepare
Appending /mnt/host/source/src/scripts/sdk_container/src/third_party/coreos-overlay to PORTDIR_OVERLAY...
 * Running stacked hooks for pre_pkg_setup
 *    sysroot_build_bin_dir ...                                                                                                                        [ ok ]
 * Checking whether python3_11 is suitable ...
 *   dev-lang/python:3.11 ...                                                                                                                          [ ok ]
 * Using python3.11 to build (via PYTHON_COMPAT iteration)
>>> Unpacking source...
 * Repository id: flatcar_init.git
 * To override fetched repository properties, use:
 *   EGIT_OVERRIDE_REPO_FLATCAR_INIT
 *   EGIT_OVERRIDE_BRANCH_FLATCAR_INIT
 *   EGIT_OVERRIDE_COMMIT_FLATCAR_INIT
 *   EGIT_OVERRIDE_COMMIT_DATE_FLATCAR_INIT
 *
 * Fetching https://github.com/flatcar/init.git ...
git fetch https://github.com/flatcar/init.git +refs/heads/flatcar-4081-backport:refs/heads/flatcar-4081-backport
git update-ref --no-deref refs/git-r3/coreos-base/coreos-init/0/__main__ 0900245444ab5a4af480805ab51986bbd58ffc7f
 * Checking out https://github.com/flatcar/init.git to /var/tmp/portage/coreos-base/coreos-init-0.0.1-r196/work/coreos-init-0.0.1 ...
git checkout --quiet 0900245444ab5a4af480805ab51986bbd58ffc7f
GIT update -->
   repository:               https://github.com/flatcar/init.git
   at the commit:            0900245444ab5a4af480805ab51986bbd58ffc7f
>>> Source unpacked in /var/tmp/portage/coreos-base/coreos-init-0.0.1-r196/work
>>> Preparing source in /var/tmp/portage/coreos-base/coreos-init-0.0.1-r196/work/coreos-init-0.0.1 ...
>>> Source prepared.

before (or CI: http://localhost:8080/job/container/job/packages/8837/consoleFull):

$ ebuild coreos-init-0.0.1-r196.ebuild clean prepare
Appending /mnt/host/source/src/scripts/sdk_container/src/third_party/coreos-overlay to PORTDIR_OVERLAY...
 * Running stacked hooks for pre_pkg_setup
 *    sysroot_build_bin_dir ...                                                                                                                        [ ok ]
 * Checking whether python3_11 is suitable ...
 *   dev-lang/python:3.11 ...                                                                                                                          [ ok ]
 * Using python3.11 to build (via PYTHON_COMPAT iteration)
>>> Unpacking source...
Initialized empty Git repository in /mnt/host/source/.cache/distfiles/git3-src/flatcar_init.git/
 * Repository id: flatcar_init.git
 * To override fetched repository properties, use:
 *   EGIT_OVERRIDE_REPO_FLATCAR_INIT
 *   EGIT_OVERRIDE_BRANCH_FLATCAR_INIT
 *   EGIT_OVERRIDE_COMMIT_FLATCAR_INIT
 *   EGIT_OVERRIDE_COMMIT_DATE_FLATCAR_INIT
 *
 * Fetching https://github.com/flatcar/init.git ...
git fetch https://github.com/flatcar/init.git +HEAD:refs/git-r3/HEAD
remote: Enumerating objects: 2649, done.
remote: Counting objects: 100% (290/290), done.
remote: Compressing objects: 100% (104/104), done.
remote: Total 2649 (delta 212), reused 188 (delta 186), pack-reused 2359 (from 3)
Receiving objects: 100% (2649/2649), 678.39 KiB | 5.95 MiB/s, done.
Resolving deltas: 100% (1302/1302), done.
From https://github.com/flatcar/init
 * [new ref]         HEAD       -> refs/git-r3/HEAD
git update-ref --no-deref refs/git-r3/coreos-base/coreos-init/0/__main__ 0900245444ab5a4af480805ab51986bbd58ffc7f
fatal: update_ref failed for ref 'refs/git-r3/coreos-base/coreos-init/0/__main__': cannot update ref 'refs/git-r3/coreos-base/coreos-init/0/__main__': trying to write ref 'refs/git-r3/coreos-base/coreos-init/0/__main__' with nonexistent object 0900245444ab5a4af480805ab51986bbd58ffc7f
 * ERROR: coreos-base/coreos-init-0.0.1-r196::coreos-overlay failed (unpack phase):
 *   Referencing 0900245444ab5a4af480805ab51986bbd58ffc7f failed (wrong ref?).
 *
 * Call stack:
 *     ebuild.sh, line  136:  Called src_unpack
 *   environment, line 3187:  Called git-r3_src_unpack
 *   environment, line 2398:  Called git-r3_src_fetch
 *   environment, line 2392:  Called git-r3_fetch
 *   environment, line 2279:  Called die
 * The specific snippet of code:
 *                   die "Referencing ${remote_ref} failed (wrong ref?).";
 *
 * If you need support, post the output of `emerge --info '=coreos-base/coreos-init-0.0.1-r196::coreos-overlay'`,
 * the complete build log and the output of `emerge -pqv '=coreos-base/coreos-init-0.0.1-r196::coreos-overlay'`.
 * The complete build log is located at '/var/log/portage/coreos-base:coreos-init-0.0.1-r196:20250311-084718.log'.
 * For convenience, a symlink to the build log is located at '/var/tmp/portage/coreos-base/coreos-init-0.0.1-r196/temp/build.log'.
 * The ebuild environment file is located at '/var/tmp/portage/coreos-base/coreos-init-0.0.1-r196/temp/environment'.
 * Working directory: '/var/tmp/portage/coreos-base/coreos-init-0.0.1-r196/work'
 * S: '/var/tmp/portage/coreos-base/coreos-init-0.0.1-r196/work/coreos-init-0.0.1'

(or see CI)

This PR is the LTS version but it has to be adapted and backported to:

• flatcar-4230
• flatcar-4186
• flatcar-4152

CI (OK at least the coreos-init emerging is OK): http://localhost:8080/job/container/job/packages_all_arches/5539/cldsv/

[tormath1]

"Cherry-picked" to:

• flatcar-4230
• flatcar-4186
• flatcar-4152

[github-actions]

Build action triggered: https://github.com/flatcar/scripts/actions/runs/13787795143