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=0e392dc35cb350f6f0986d816e315d2e38cdef78'>root</a>/<a href='/guix/log/doc?id=0e392dc35cb350f6f0986d816e315d2e38cdef78'>doc</a>/<a href='/guix/log/doc/images?id=0e392dc35cb350f6f0986d816e315d2e38cdef78'>images</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/doc/images?id=0e392dc35cb350f6f0986d816e315d2e38cdef78&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2020-05-22 16:11:52 +0200'>2020-05-22</span></td><td><a href='/guix/commit/doc/images?id=cd5d5f53228fd5bf96d9f790aa2606ae71fa68d7'>doc: Update 'Bootstrapping' for further binary seed reduction.</a><span class='msg-avail'>...<span class='msg-tooltip'>* doc/images/gcc-core-mesboot0-graph.dot: New image, replacing
* doc/images/gcc-mesboot0-bag-graph.dot: ... remove file.
* doc/local.mk (DOT_FILES): Update for new image file.
* doc/guix.texi (Reduced Binary Seed Bootstrap): Use it in updated description
of further reduction of the trusted computing base.
</span></span></td><td>Jan Nieuwenhuizen</td></tr>
ès</td></tr>
<tr><td><span title='2019-06-05 17:27:22 +0200'>2019-06-05</span></td><td><a href='/guix/commit/etc/guix-publish.service.in?id=a5ca4a63426f5e24c13b93bde95511e9d89757f5'>etc: Fix GUIX_LOCPATH quoting in 'guix-publish.service' file.</a><span class='msg-avail'>...<span class='msg-tooltip'>This is a followup to 579d17b70dac067f8194ede46513400b91ac136a.

* etc/guix-publish.service.in (Environment): Move GUIX_LOCPATH inside
the quotes.
</span></span></td><td>Jack Hill</td></tr>
<tr><td><span title='2019-05-13 23:46:08 +0200'>2019-05-13</span></td><td><a href='/guix/commit/etc/guix-publish.service.in?id=489d6c0dc03f1d95a3fefa6301f36cac9b50b2c3'>Set 'LC_ALL=en_US.utf8' in systemd '.service' files.</a><span class='msg-avail'>...<span class='msg-tooltip'>Fixes &lt;https://bugs.gnu.org/35671&gt;.

* etc/guix-daemon.service.in (Environment): Quote the 'GUIX_LOCPATH'
value; add 'LC_ALL'.
* etc/guix-publish.service.in (Environment): Likewise.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2018-11-23 15:42:01 +0100'>2018-11-23</span></td><td><a href='/guix/commit/etc/guix-publish.service.in?id=e9926f80c6553fde50ce1fcfd38d6370f841efd2'>build: Binary tarball now populates the "current-guix" profile.</a><span class='msg-avail'>...<span class='msg-tooltip'>* Makefile.am (guix-binary.%.tar.xz): Pass
'--profile-name=current-guix'.  Remove glibc and glibc-utf8-locales.
* doc/guix.texi (Binary Installation): Update accordingly.
* etc/guix-install.sh
* etc/guix-install.sh (sys_create_store, sys_enable_guix_daemon)
(sys_authorize_build_farms): Likewise.
* etc/guix-publish.conf.in, etc/guix-publish.service.in,
etc/guix-daemon.conf.in, etc/guix-daemon.service.in: Update file names
accordingly.
</span></span></td><td>Ludovic Courtès</td></tr>