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=08b34ca0fc915ea440b069ec8cd18c142a5a5523'>root</a>/<a href='/guix/log/gnu?id=08b34ca0fc915ea440b069ec8cd18c142a5a5523'>gnu</a>/<a href='/guix/log/gnu/services?id=08b34ca0fc915ea440b069ec8cd18c142a5a5523'>services</a>/<a href='/guix/log/gnu/services/ldap.scm?id=08b34ca0fc915ea440b069ec8cd18c142a5a5523'>ldap.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/services/ldap.scm?id=08b34ca0fc915ea440b069ec8cd18c142a5a5523&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2022-12-14 22:56:00 +0100'>2022-12-14</span></td><td><a href='/guix/commit/gnu/services/ldap.scm?id=82c511dd5489bd7a2cbcd0313b9f54f9d7f166d2'>gnu: slapd-configuration: Update default for run-dir.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/services/ldap.scm (slapd-configuration): Update default value for
run-dir to match defaults of 389-ds-base package.
* doc/guix.texi: Update documentation.
</span></span></td><td>Ricardo Wurmus</td></tr>
<tr><td><span title='2022-12-14 20:55:04 +0100'>2022-12-14</span></td><td><a href='/guix/commit/gnu/services/ldap.scm?id=c6f81ff7a6a527b5a14189a2c359b981ddba43bc'>gnu: Add directory-server-service-type.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/services/ldap.scm: New file.
* gnu/local.mk (GNU_SYSTEM_MODULES): Add it.
* doc/guix.texi (LDAP Services): Document it.
</span></span></td><td>Ricardo Wurmus</td></tr>