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=ec9c5a8ff5da1dc08759fbca467a74fe8f5bd9db'>root</a>/<a href='/guix/log/manifest.scm?id=ec9c5a8ff5da1dc08759fbca467a74fe8f5bd9db'>manifest.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/manifest.scm?id=ec9c5a8ff5da1dc08759fbca467a74fe8f5bd9db&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2024-04-02 23:28:58 +0200'>2024-04-02</span></td><td><a href='/guix/commit/manifest.scm?id=049273bb8c1ea3d6402db646312acdc4abf4678a'>maint: Add perl to the manifest.</a><span class='msg-avail'>...<span class='msg-tooltip'>* manifest.scm: Add perl.

Change-Id: Ie70cea1eb4d62f2a649292209391a92abdae2288
</span></span></td><td>Janneke Nieuwenhuizen</td></tr>
<tr><td><span title='2024-01-31 09:07:25 +0100'>2024-01-31</span></td><td><a href='/guix/commit/manifest.scm?id=66dd088d3c3404f5cbe2d4d4c5e8f93d184703b0'>maint: Add gnupg to the manifest.</a><span class='msg-avail'>...<span class='msg-tooltip'>* manifest.scm: Add gnupg.

Change-Id: Id5e90f87e5c3a07aa3e49afa97cc0b6d3ce71b41
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2023-09-18 22:12:39 +0200'>2023-09-18</span></td><td><a href='/guix/commit/manifest.scm?id=7bf12820f61179900f9d1f753acf91fd33724976'>maint: Support `guix shell' in Guix's git archive with manifest.scm.</a><span class='msg-avail'>...<span class='msg-tooltip'>* manifest.scm: New file.
* Makefile.am (EXTRA_DIST): Add it.
* doc/contributing.texi (Building from Git): Mention using it.
</span></span></td><td>Janneke Nieuwenhuizen</td></tr>