GitLab CI: move back to only 2 stages, build and osxcross

.gitlab-ci.yml

.gitlab/ci/jobs/alpine-3-gcc-makefile.yml

.gitlab/ci/jobs/alpine-3-gcc.yml

.gitlab/ci/jobs/batocera-arm64-makefile.yml

.gitlab/ci/jobs/batocera-arm64.yml

.gitlab/ci/jobs/debian-oldstable-amd64-makefile.yml

.gitlab/ci/jobs/debian-oldstable-amd64.yml

.gitlab/ci/jobs/debian-oldstable-arm64-makefile.yml

.gitlab/ci/jobs/debian-oldstable-arm64.yml

.gitlab/ci/jobs/debian-stable-amd64-makefile.yml

.gitlab/ci/jobs/debian-stable-amd64.yml

.gitlab/ci/jobs/debian-stable-arm64-makefile.yml

.gitlab/ci/jobs/debian-stable-arm64.yml

.gitlab/ci/jobs/debian-stable-clang-amd64.yml

.gitlab/ci/jobs/debian-stable-i386-makefile.yml

.gitlab/ci/jobs/debian-stable-i386.yml

.gitlab/ci/jobs/debian-testing-gcc-amd64-makefile.yml

.gitlab/ci/jobs/debian-testing-gcc-amd64.yml

.gitlab/ci/jobs/macos-arm64.yml

.gitlab/ci/jobs/macos-x86_64.yml