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=5a1c16fa18d21f14dfb968c1803a3344ae7b4a02'>root</a>/<a href='/guix/log/gnu?id=5a1c16fa18d21f14dfb968c1803a3344ae7b4a02'>gnu</a>/<a href='/guix/log/gnu/machine.scm?id=5a1c16fa18d21f14dfb968c1803a3344ae7b4a02'>machine.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/machine.scm?id=5a1c16fa18d21f14dfb968c1803a3344ae7b4a02&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2022-02-08 13:34:02 +0100'>2022-02-08</span></td><td><a href='/guix/commit/gnu/machine.scm?id=ab7114191d4599e36958c2ec18491618bf0cc6a9'>gnu: Fix typo.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/machine.scm: Fix typo in top-level comment.

Signed-off-by: Ludovic Courtès &lt;ludo@gnu.org&gt;
</span></span></td><td>jgart</td></tr>