Trac #34152: Remove remaining dependencies of bootstrap on gettext (AC_LIB_RPATH etc.)

**Background**: `./bootstrap` needs about 112 KB of m4 and shell code
from `gnulib`: https://www.gnu.org/software/gnulib
Before #29549, these files were copied from a system-wide installation
of `gettext` (which uses `gnulib`): https://www.gnu.org/software/gettext

As opposed to `gettext`, `gnulib` does not make releases, and many
systems don't package `gnulib` at all. Thus one cannot uniformly rely on
`gnulib` being already installed. This essentially leaves two options
for using `gnulib` in Sage - copy said 112K into the Sage git tree, or
provide `gnulib` as a Sage pseudo-package (pseudo, due to the chicken vs
egg issue: one cannot just make it an ordinary spkg - it needs to be
used by `bootstrap`).

Who needs to run `bootstrap` and where:
- Any developer who switches to a branch that makes an SPKG upgrade or
other changes to the build system, on their development machine.
- Our
[[https://doc.sagemath.org/html/en/developer/portability_testing.html
#testing-sage-on-a-different-platform-using-docker|portability
testsuite]], run locally using `tox -e docker-...` and on GH Actions, in
the Docker container for the tested platform.

Who does not need to run `bootstrap`:
- Users who only build released versions from tarballs - because they
come pre-bootstrapped
- Users who only build released versions from a git clone - because Sage
falls back to downloading a tarball of the `configure` SPKG.

--------

**History**: #29549 intended to remove the dependency of `bootstrap` on
`gettext`. #29549 made it possible to run `bootstrap` on the `manylinux`
platforms needed by cibuildwheel (#33800).

The branch of #29549 followed "copy files" approach. However, some files
that `gnulib-tool` added were left out from the commit, so it breaks on
machines on which `gettext` is missing completely, as reported in
https://groups.google.com/g/sage-release/c/FezzF5Q7Wt4/m/xyxVTaYgBAAJ

-------

**This ticket**:
Here we complete the task and remove `gettext` from various `distros/`
files etc.

Two approaches have been proposed:

mkoeppe ("copy files") : [[https://github.com/sagemath/sagetrac-
mirror/compare/develop...4011cc4608|Branch
u/mkoeppe/fix_broken_bootstrap__ac_lib_rpath_etc__ @ 4011cc4608]]
- Follows approach 3 of the
[[https://www.gnu.org/software/gnulib/manual/html_node/VCS-
Issues.html|Gnulib manual section 'Integration with Version Control
Systems']].
- 5 files, in `config/` and `m4/`, total 112 KB, have been imported by
using [[https://www.gnu.org/software/gnulib/manual/html_node/Initial-
import.html|`gnulib-tool import iconv`]] and committed to the branch.
- Matches our practice with imported files
[[https://github.com/sagemath/sage/tree/develop/m4|`m4/ax_*.m4`]] from
[[https://www.gnu.org/software/autoconf-archive/The-Macros.html
|autoconf-archive]]. Different from our practice with SPKGs because the
files are needed to generate the `configure` script.
- Introduces no new dependency.
- Burden on a developer who authors an update ticket for these files:
Obtain gnulib by cloning the repo, then re-run `gnulib-tool import`,
remove unneeded files (that's where #29549 went wrong), commit the
changes. (Updates are expected to be necessary only very rarely.)
- Burden on users and other developers: None.
- dimpase's criticism of this approach: "gnulib's code is not Sage's
code, it has no place in Sage git tree; this way, updating the imported
gnulib files is tricky and error-prone by design".

dimpase ("Sage pseudo-package"): https://github.com/sagemath/sagetrac-
mirror/compare/develop...u/dimpase/config/gnulib
- Follows approach 2(C) of the
[[https://www.gnu.org/software/gnulib/manual/html_node/VCS-
Issues.html|Gnulib manual section 'Integration with Version Control
Systems']], but instead of using Gnulib's
[[https://www.gnu.org/software/gnulib/manual/html_node/Developer-
tools.html|Programs for developing in Git checkouts]], implements its
own script (making checkout much faster, as full `gnulib` checkout is
250 MB).
- Introduces a new (although one can't really do Sage development
without `git` installed) dependency on `git` and on availability of
internet connection at the first run of `./bootstrap` in a tree, to pull
83 MB (fair to say that internet is needed for Sage development a lot,
anyway).
- Burden on a developer who authors an update ticket for these files:
Edit the `bootstrap` file to change the commit hash, verify that the
list of files removed by `make bootstrap-clean` is still correct, commit
this change
- Burden on other users: a pseudo-package needs to be installed once
(and updated, automatically)
- mkoeppe's criticism of this approach: "Having `bootstrap` operate a
multi-megabyte git clone (on the 1st install and when there's a change
of the gnulib commit hash) in the `upstream/` directory increases
complexity for no benefit."

hybrid ("copy files, spkg-src script for maintenance"):
[[https://github.com/sagemath/sagetrac-
mirror/compare/develop...u/mkoeppe/config/gnulib|Branch
u/mkoeppe/config/gnulib]]
- Resolves the criticism on the "copy files" approach: "updating the
imported gnulib files" is now assisted by the `spkg-src` script (adapted
from dimpase's branch)
- Resolves the criticism on the "Sage pseudo-package" approach: "operate
a multi-megabyte git clone (on the 1st install and when there's a change
of the gnulib commit hash)" is only done by authors of tickets that
update gnulib, not by general users of `bootstrap`.

-------

'''Voting took place at https://groups.google.com/g/sage-
devel/c/E2qstbWXC7g'''

-------

To test: For example `tox -r -e local-homebrew-macos-minimal --
config.status`

URL: https://trac.sagemath.org/34152
Reported by: mkoeppe
Ticket author(s): Matthias Koeppe, Dima Pasechnik
Reviewer(s): François Bissey, ​Dima Pasechnik, Matthias Koeppe, Kwankyu
Lee

Author: Release Manager

.homebrew-build-env

@@ -2,7 +2,7 @@
 # that activate keg-only homebrew package installations
 
 HOMEBREW=`brew --prefix` || return 1
-for l in gettext bzip2 texinfo polymake; do
+for l in bzip2 texinfo polymake; do
     if [ -d "$HOMEBREW/opt/$l/bin" ]; then
         PATH="$HOMEBREW/opt/$l/bin:$PATH"
     fi
@@ -39,7 +39,7 @@ for l in "gcc/lib/gcc/11 gcc/lib/gcc/10 gcc/lib/gcc/9"; do
 done
 export LIBRARY_PATH
 export CPATH
-for l in gettext; do
+for l in ; do
     if [ -d "$HOMEBREW/opt/$l/share/aclocal" ]; then
         ACLOCAL_PATH="$HOMEBREW/opt/$l/share/aclocal:$ACLOCAL_PATH"
     fi

build/pkgs/_bootstrap/distros/arch.txt

@@ -1,4 +1,4 @@
 # Packages needed for ./bootstrap
-gettext autoconf automake libtool
+autoconf automake libtool
 # Otherwise: Error: could not locate the pkg-config autoconf macros. These are
 pkg-config

build/pkgs/_bootstrap/distros/conda.txt

@@ -1,2 +1,2 @@
 # Packages needed for ./bootstrap
-gettext autoconf automake libtool
+autoconf automake libtool

build/pkgs/_bootstrap/distros/cygwin.txt

@@ -1,2 +1,2 @@
 # Packages needed for ./bootstrap
-gettext-devel autoconf automake libtool
+autoconf automake libtool

build/pkgs/_bootstrap/distros/debian.txt

@@ -1,5 +1,4 @@
 # Packages needed for ./bootstrap
-gettext
 autoconf
 automake
 libtool

build/pkgs/_bootstrap/distros/fedora.txt

@@ -1,4 +1,4 @@
 # Packages needed for ./bootstrap
-gettext-devel autoconf automake libtool
+autoconf automake libtool
 # Fedora 26 needs:
 pkg-config

build/pkgs/_bootstrap/distros/freebsd.txt

@@ -1,2 +1,2 @@
 # Packages needed for ./bootstrap
-gettext autoconf automake libtool pkg-config
+autoconf automake libtool pkg-config

build/pkgs/_bootstrap/distros/homebrew.txt

@@ -1,2 +1,2 @@
 # Packages needed for ./bootstrap
-gettext autoconf automake libtool pkg-config
+autoconf automake libtool pkg-config

build/pkgs/_bootstrap/distros/nix.txt

@@ -1,2 +1,2 @@
 # Packages needed for ./bootstrap
-gettext autoconf automake libtool pkg-config
+autoconf automake libtool pkg-config

build/pkgs/_bootstrap/distros/opensuse.txt

@@ -1,5 +1,4 @@
 # Packages needed for ./bootstrap
-gettext-tools
 autoconf
 automake
 libtool