Move build/sage_bootstrap to pkgs/sage-bootstrap/sage_bootstrap

[mkoeppe]

We transform build/sage_bootstrap to a new pip-installable distribution sage-bootstrap (with source dir SAGE_ROOT/pkgs/sage-bootstrap).

Other bits from SAGE_ROOT and build/ become package data of this distribution, for now via symlinks.

In:

SAGE_ROOT
- pkgs
  - sage-bootstrap
    - bin
      - sage-apply-patches
      - sage-bootstrap-python
      - sage-dist-helpers
      - sage-package
      - sage-pip-*install
      - sage-print-system-package-command
      - sage-spkg*
      - sage-uncompress-spkg
      - sage-venv
    - pyproject.toml
    - sage_bootstrap/
      - pkgs/        -> SAGE_ROOT/build/pkgs
      - m4/          -> SAGE_ROOT/m4
- build/pkgs
  - sage_bootstrap
     - bootstrap

Out:

• parts of the specific config / build system of the Sage distribution: configure.ac, build/make, build/bin/sage-site, build/bin/sage-logger, build/bin/sage-starts, build/bin/sage-sdist, build/bin/sage-site
• monorepo driver: SAGE_ROOT/bootstrap, tox.ini, .ci/write-dockerfile.sh,

We put an sdist of the distribution 'sage-bootstrap' on PyPI, to give users easy access to commands such as sage-print-system-package-command. This can be useful for other projects that want to generate system package advice.

Depends on #31577

CC: @dimpase @jhpalmieri

Component: build

Work Issues: Set PYTHONPATH wherever PATH is set to include build/bin

Author: Matthias Koeppe

Issue created by migration from https://trac.sagemath.org/ticket/31662

[mkoeppe]

Branch: u/mkoeppe/rename_sage_root_build_to_sage_root_pkgs_sage_bootstrap

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1. New commits:

25eadf1

pkgs/sage-bootstrap/setup.cfg: New

[sagetrac-git]

Commit: 25eadf1

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1. New commits:

05b202b	Make build/pkgs a symlink to sage_bootstrap package_data
2a5f45e	pkgs/sage-bootstrap/sage_bootstrap/sage_root_source: Move it all here, symlink to SAGE_ROOT

[sagetrac-git]

Changed commit from 25eadf1 to 2a5f45e

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1. This was a forced push. New commits:

830d804

pkgs/sage-bootstrap/sage_bootstrap: Move here from build/sage_bootstrap

[sagetrac-git]

Changed commit from 2a5f45e to 830d804

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1. New commits:

632678c

pkgs/sage-bootstrap: Use setuptools, add metadata

[sagetrac-git]

Changed commit from 830d804 to 632678c

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1. New commits:

07955b0

build/pkgs/sage_bootstrap: New

[sagetrac-git]

Changed commit from 632678c to 07955b0

[mkoeppe]

Work Issues: Set PYTHONPATH wherever PATH is set to include build/bin

[mkoeppe]

Author: Matthias Koeppe

[mkoeppe]

Removed branch from issue description. Replaced by PR #38587