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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<tr><td><span title='2022-02-18 14:14:38 +0100'>2022-02-18</span></td><td><a href='/guix/commit/tests/guix-build.sh?id=0ca26437cb36822f9f74ee1a6dbc714477378b13'>guix build: Warn when attempting to build an unsupported package.</a><span class='msg-avail'>...<span class='msg-tooltip'>Fixes &lt;https://issues.guix.gnu.org/51801&gt;.
Reported by Maxim Cournoyer &lt;maxim.cournoyer@gmail.com&gt;.

* guix/scripts/build.scm (options-&gt;derivations)[warn-if-unsupported]:
New procedure.
[compute-derivation]: Use it.
* tests/guix-build.sh: Add test.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2021-11-08 09:06:14 +0200'>2021-11-08</span></td><td><a href='/guix/commit/tests/guix-build.sh?id=1c94392a13cbdf87e03a644633eb775bf45694a1'>Merge remote-tracking branch 'origin/master' into core-updates-frozen</a></td><td>Efraim Flashner</td></tr>
<tr><td><span title='2021-11-07 23:10:41 +0100'>2021-11-07</span></td><td><a href='/guix/commit/tests/guix-build.sh?id=4d59596a1c5f6b20870e619cbf67068ac7dd64ff'>ui: 'load*' correctly reports 'read-error' in all cases.</a><span class='msg-avail'>...<span class='msg-tooltip'>Previously, 'read-error' exceptions other than "missing closing paren"
would not be reported; instead, we'd directly call (exit 1) without
printing anything.

Fixes &lt;https://issues.guix.gnu.org/51463&gt;.
Reported by Alice BRENON &lt;alice.brenon@ens-lyon.fr&gt;.

* guix/ui.scm (report-load-error): Report the error without re-throwing
upon 'read-error'.
* tests/guix-build.sh: Add test.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2021-09-07 14:54:09 +0200'>2021-09-07</span></td><td><a href='/guix/commit/tests/guix-build.sh?id=445eec918332c1b8d4a6ba4baf1322e13076029b'>tests: Adjust '--with-input' test.</a><span class='msg-avail'>...<span class='msg-tooltip'>This is a followup to 09b002622e2113c2f14c11ccd43fa01fd343fb95, which
changed the dependency of graphviz from guile@2.0 to guile@3.0.

* tests/guix-build.sh: Adjust '--with-input' test.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2021-03-23 23:19:57 -0700'>2021-03-23</span></td><td><a href='/guix/commit/tests/guix-build.sh?id=a16eb6c5f97f136b678540ba61f12b2c08e43e13'>Add powerpc64le-linux as a supported Guix architecture.</a><span class='msg-avail'>...<span class='msg-tooltip'>This makes powerpc64le-linux a supported architecture for Guix, but not for
Guix System.

* Makefile.am (SUPPORTED_SYSTEMS): Add an entry for powerpc64le-linux.
* etc/guix-install.sh (chk_sys_arch): Same.
* guix/packages.scm (%supported-systems): Same.
* m4/guix.m4 (GUIX_ASSERT_SUPPORTED_SYSTEM): Same.
* tests/guix-build.sh (all_systems): Same.
</span></span></td><td>Chris Marusich</td></tr>