build/activation: Simplify the creation of /etc.

Do not add a an extraneous /etc/static layer of indirection.

* gnu/build/activation.scm (activate-etc) <realpath>: New nested procedure.
Do not create /etc/static.  Symlink instead of copy all files under /etc,
except for /etc/sudoers.

Change-Id: I8ea16d07de256482efac37d2ff9482a5f56bd585
Reviewed-by: Ludovic Courtès <ludo@gnu.org>

gnu: Add spell.

* gnu/packages/aspell.scm (spell): New variable.

Change-Id: I89333c66c23e43d4c90e6ef57203ca3a9dce78a1
Reviewed-by: Cayetano Santos <csantosb@inventati.org>

gnu: gnuastro: Update to 0.24.

* gnu/packages/astronomy.scm (gnuastro): Update to 0.24.

Change-Id: If02e9abb4bee883fa65592c6e5497a0a613981f2
Signed-off-by: Sharlatan Hellseher <sharlatanus@gmail.com>

gnu: Add python-spacetrack.

* gnu/packages/astronomy.scm (python-spacetrack): New variable.

Change-Id: I9ab6910016b5861a339ae6c2485b4d9f6712415a

gnu: Add python-orbitalpy.

* gnu/packages/astronomy.scm (python-orbitalpy): New variable.

Change-Id: I467dfb60d73263dd5ae4dbf58628a8b621519a16

gnu: Add python-represent.

* gnu/packages/python-xyz.scm (python-represent): New variable.

Change-Id: If8081edde0caf8808a1930ed648c6896ba2b3a6f

gnu: Add python-rush.

* gnu/packages/python-xyz.scm (python-rush): New variable.

Change-Id: I1e7500e63b986e33bed8eb6c1e14181eebd23463

gnu: Add python-glue-geospatial.

* gnu/packages/astronomy.scm (python-glue-geospatial): New variable.

Change-Id: Ie6529b4b80c4758e3f12e260c687e8f98b575edc

gnu: Add python-astromartini.

* gnu/packages/astronomy.scm (python-astromartini): New variable.

Change-Id: Ibea4652ba7b919a97e5791bd266bbd3d89ea3320

gnu: Add python-astrodata.

* gnu/packages/astronomy.scm (python-astrodata): New variable.

Change-Id: If3552abcddda7f44ec620778e498383894053fda

gnu: uraniborg: Update to 0.0.14.

* gnu/packages/astronomy.scm (uraniborg): Update to 0.0.14.

Change-Id: I69a5e941349225d99cd3249bf9285fcb0d8c1129

gnu: tenmon: Update to 20251101.

* gnu/packages/astronomy.scm (tenmon): Update to 20251101.

Change-Id: Ia355ff3c3aa702672d9ea55770a4c7c8bc6a88c4

gnu: tangos: Update to 1.10.0.

* gnu/packages/astronomy.scm (tangos): Update to 1.10.0.
[arguments] <test-flags>: Enable more tests.
<phases>: Add 'pre-check.
[inputs]: Remove python-sqlalchemy; add python-psycopg2, python-pymysql,
and python-sqlalchemy-2.
[native-inputs]: Remove python-pynbody-1 and python-setuptools; add
python-pynbody.

Change-Id: Ied60d7bee177266d2e8e7f8fe1471a18505e7a8b

gnu: splash: Update to 3.11.6.

* gnu/packages/astronomy.scm (splash): Update to 3.11.6.

Change-Id: Iadabcc8c3d7513ffc59b14c235aa7bcd16e305fa

gnu: phd2: Update to 2.6.13-2.7ed00ec.

* gnu/packages/astronomy.scm (phd2): Update to
7ed00ec3e05fddb81b2026a07db9431e551f150e commit.

Change-Id: I3e118c0bfb5384a820a614f56e5df442b33cca91

gnu: imppg: Update to 2.1.0.

* gnu/packages/astronomy.scm (imppg): Update to 2.1.0.
[arguments] <tests?>: Enable.

Change-Id: Ie2313794e5a53e7b50272dbbaff8cf7fd9a8e238

gnu: celestia-content: Update to 0.0.0-2.e707d64.

* gnu/packages/astronomy.scm (celestia-content): Update to
e707d64080558860ea647f72f25571f3f9b05f53 commit.

Change-Id: I186961bb015e39148acabf4682d355edea6b1862

gnu: python-spisea: Update to 2.1.15.

* gnu/packages/astronomy.scm (python-spisea): Update to 2.1.15.
[arguments] <phases>: Remove 'preparations; add 'fix-setup.cfg, and
'set-version.
[native-inputs]: Remove python-wheel.

Change-Id: I27f5f846c3e9bc841ba259d7522909c91b40d6f6

gnu: python-pyxsim: Update to 4.4.3.

* gnu/packages/astronomy.scm (python-pyxsim): Update to 4.4.3.
[arguments] <phases>: Remove 'set-home.
[native-inputs]: Remove python-wheel.

Change-Id: I27f857dcd637b5223a0381206ebd032619d587b2

gnu: python-fitsio: Update to 1.3.0.

* gnu/packages/astronomy.scm (python-fitsio): Update to 1.3.0.
[source] <snippet>: Addjust to new cfitsio version.

Change-Id: I55585e641ebebb2ff79e5a5b10e054daf808eb2a