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
--- a/localedata/Makefile
+++ b/localedata/Makefile
@@ -176,7 +176,8 @@
 else
 install-others := $(addprefix $(inst_i18ndir)/, \
 			      $(addsuffix .gz, $(charmaps)) \
-			      $(locales))
+			      $(locales)) \
+                   $(inst_i18ndir)/SUPPORTED
 endif
 
 tests: $(objdir)/iconvdata/gconv-modules
@@ -401,6 +402,14 @@
 
 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=c8312a6d070677909130c227e9a5bbcaa6a57bfe&amp;showmsg=1'>root</a>/<a href='/guix/log/gnu?id=c8312a6d070677909130c227e9a5bbcaa6a57bfe&amp;showmsg=1'>gnu</a>/<a href='/guix/log/gnu/tests?id=c8312a6d070677909130c227e9a5bbcaa6a57bfe&amp;showmsg=1'>tests</a>/<a href='/guix/log/gnu/tests/version-control.scm?id=c8312a6d070677909130c227e9a5bbcaa6a57bfe&amp;showmsg=1'>version-control.scm</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/gnu/tests/version-control.scm?id=c8312a6d070677909130c227e9a5bbcaa6a57bfe'>Collapse</a>)</th><th class='left'>Author</th></tr>
<tr class='logheader'><td><span title='2022-04-29 18:07:17 +0200'>2022-04-29</span></td><td class='logsubject'><a href='/guix/commit/gnu/tests/version-control.scm?id=73eeeeafbb0765f76834b53c9fe6cf3c8f740840'>tests: Avoid starting services to check whether they're running.</a></td><td>Ludovic Courtès</td></tr>
<tr class='nohover-highlight'><td/><td colspan='3' class='logmsg'>
Fixes a regression introduced in the Shepherd 0.9.0 whereby clients can
start a service that is already being started, leading to two instances
of the process (and usually failure of the second attempt to start it).

Partly fixes &lt;https://issues.guix.gnu.org/54786&gt;.
Reported by Mathieu Othacehe.

* gnu/tests/version-control.scm (run-cgit-test)
["nginx running", "fcgiwrap running"]: Wail for a file/TCP port instead
of starting the service.
(run-git-http-test)["nginx running"]: Likewise.
(run-gitile-test)["nginx running"]: Likewise.


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