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.old b/localedata/Makefile
index 34877c0..a61d9b9 100644
--- a/localedata/Makefile.old
+++ b/localedata/Makefile
@@ -91,7 +91,8 @@ endif
 # Files to install.
 install-others := $(addprefix $(inst_i18ndir)/, \
 			      $(addsuffix .gz, $(charmaps)) \
-			      $(locales))
+			      $(locales)) \
+                   $(inst_i18ndir)/SUPPORTED
 
 tests: $(objdir)/iconvdata/gconv-modules
 
@@ -195,6 +196,14 @@ 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 $@
+
 INSTALL-SUPPORTED-LOCALES=$(addprefix install-, $(SUPPORTED-LOCALES))
 
 # Sometimes the whole collection of locale files should be installed.
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<tr><td><span title='2022-04-29 18:07:17 +0200'>2022-04-29</span></td><td><a href='/guix/commit/tests/publish.scm?id=c1719a0adf3fa7611b56ca4d75b3ac8cf5c9c8ac'>publish: Send uncached narinfo replies from the main thread.</a><span class='msg-avail'>...<span class='msg-tooltip'>Fixes &lt;https://issues.guix.gnu.org/54723&gt;.
Reported by Guillaume Le Vaillant &lt;glv@posteo.net&gt;.

Regression introduced in f743f2046be2c5a338ab871ae8666d8f6de7440b.

With commit f743f2046be2c5a338ab871ae8666d8f6de7440b, responses to
pipelined GETs would end up being written concurrently by many threads.
Thus the body of those responses could be interleaved and garbled.

* guix/scripts/publish.scm: Revert
f743f2046be2c5a338ab871ae8666d8f6de7440b.
* tests/publish.scm ("/*.narinfo pipeline"): New test.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2022-02-14 11:23:56 +0100'>2022-02-14</span></td><td><a href='/guix/commit/tests/publish.scm?id=6adce1538d2df6fa2d68abc13ae94e2fa826d124'>publish: Do not sign the URL/Compression/FileSize narinfo fields.</a><span class='msg-avail'>...<span class='msg-tooltip'>This will allow mirror operators to alter these non-normative bits of a
narinfo without having to resign narinfos.

* guix/scripts/publish.scm (narinfo-string): Remove
URL/Compression/FileSize from BASE-INFO.  Move them after "Signature".
* tests/publish.scm ("/*.narinfo")
("/*.narinfo with properly encoded '+' sign")
("/*.narinfo with lzip + gzip")
("with cache, lzip + gzip"): Adjust accordingly.
* tests/substitute.scm ("query narinfo with signature over relevant subset"):
New test.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2022-01-19 22:07:54 +0100'>2022-01-19</span></td><td><a href='/guix/commit/tests/publish.scm?id=435ffae2f29ecaa94f3aca835d79e222bc1263d5'>tests: Adjust to gzip as the default log compression.</a><span class='msg-avail'>...<span class='msg-tooltip'>This is a followup to 575e52ac2b090fd194086e9c1c53bbf8055acbc2.

* tests/publish.scm ("/log/NAME"): Expect a gzip-encoded log.
</span></span></td><td>Ludovic Courtès</td></tr>