This patch is taken from debian's glibc package (generate-supported.mk).
It install the localedata/SUPPORTED file of the glibc. This file lists
all the supported locales of the glibc.

diff --git a/localedata/Makefile b/localedata/Makefile
index 65079f9eb8..14818f84e0 100644
--- a/localedata/Makefile
+++ b/localedata/Makefile
@@ -169,7 +169,8 @@ endif
 # Files to install.
 install-others := $(addprefix $(inst_i18ndir)/, \
 			      $(addsuffix .gz, $(charmaps)) \
-			      $(locales))
+			      $(locales)) \
+                   $(inst_i18ndir)/SUPPORTED
 
 tests: $(objdir)/iconvdata/gconv-modules
 
@@ -380,6 +381,14 @@ endif
 
 include SUPPORTED
 
+$(inst_i18ndir)/SUPPORTED: SUPPORTED $(+force)
+	for locale in $(SUPPORTED-LOCALES); do \
+		[ $$locale = true ] && continue; \
+		echo $$locale | sed 's,/, ,' >> LOCALES; \
+	done
+	$(make-target-directory)
+	$(INSTALL_DATA) LOCALES $@
+
 INSTALL-SUPPORTED-LOCALE-ARCHIVE=$(addprefix install-archive-, $(SUPPORTED-LOCALES))
 INSTALL-SUPPORTED-LOCALE-FILES=$(addprefix install-files-, $(SUPPORTED-LOCALES))
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<div class='path'>path: <a href='/guix/log/?id=63a2243d58d025788941a60e6296f174828f7acf'>root</a>/<a href='/guix/log/etc?id=63a2243d58d025788941a60e6296f174828f7acf'>etc</a>/<a href='/guix/log/etc/init.d?id=63a2243d58d025788941a60e6296f174828f7acf'>init.d</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/etc/init.d?id=63a2243d58d025788941a60e6296f174828f7acf&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2024-06-26 22:59:55 +0200'>2024-06-26</span></td><td><a href='/guix/commit/etc/init.d?id=d11b96eb5493231a5a35045505ff8ae8aa746b8e'>etc: Add explicit ‘--substitute-urls’ in guix-daemon service files.</a><span class='msg-avail'>...<span class='msg-tooltip'>Having substitute URLs explicitly listed in the service startup file
makes it clearer what should be modified to permanently change the list
of substitute URLs.

* config-daemon.ac: Rename ‘guix_substitute_urls’ to
‘GUIX_SUBSTITUTE_URLS’ and substitute it.
* nix/local.mk (etc/guix-%.service, etc/init.d/guix-daemon)
(etc/guix-%.conf): Substitute it.
* etc/guix-daemon.conf.in, etc/guix-daemon.service.in,
etc/init.d/guix-daemon.in: Add an explicit ‘--substitute-urls’ option.

Change-Id: Ie491b7fab5c42e54dca582801c03805a85de2bf9
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2021-07-07 23:54:20 -0400'>2021-07-07</span></td><td><a href='/guix/commit/etc/init.d?id=4cbe0127a668cbcc64087c5d311308b59d39b104'>guix-install.sh: Prompt for configuring substitutes discovery.</a><span class='msg-avail'>...<span class='msg-tooltip'>Also ensure prompt_yes_no always print the message with a trailing space,
which is more pleasing to the eye.

* etc/guix-daemon.conf.in &lt;--discover=no&gt;: New guix-daemon option.
* etc/guix-daemon.service.in: Likewise.
* etc/init.d/guix-daemon.in: Likewise.
* etc/openrc/guix-daemon.in: Likewise.
* etc/guix-install.sh (configure_substitute_discovery): New procedure.
(sys_enable_guix_daemon): Ask the user whether automatic substitute discovery
should be enabled.  Set the '--discover' argument accordingly.
(prompt_yes_no): Add a trailing space to the message.
(sys_authorize_build_farms): Remove trailing space from the message argument.
* NEWS (Distribution): Add news.
</span></span></td><td>Maxim Cournoyer</td></tr>