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))
 
='sub right'></td></tr></table>
<table class='tabs'><tr><td>
<a href='/guix/about/'>about</a><a href='/guix/'>summary</a><a href='/guix/refs/?id=ab9f9b582e510e3d1133ec29242e70fca1d2997a'>refs</a><a class='active' href='/guix/log/gnu/packages/patches/aegis-test-fixup-2.patch'>log</a><a href='/guix/tree/gnu/packages/patches/aegis-test-fixup-2.patch?id=ab9f9b582e510e3d1133ec29242e70fca1d2997a'>tree</a><a href='/guix/commit/gnu/packages/patches/aegis-test-fixup-2.patch?id=ab9f9b582e510e3d1133ec29242e70fca1d2997a'>commit</a><a href='/guix/diff/gnu/packages/patches/aegis-test-fixup-2.patch?id=ab9f9b582e510e3d1133ec29242e70fca1d2997a'>diff</a></td><td class='form'><form class='right' method='get' action='/guix/log/gnu/packages/patches/aegis-test-fixup-2.patch'>
<input type='hidden' name='id' value='ab9f9b582e510e3d1133ec29242e70fca1d2997a'/><select name='qt'>
<option value='grep'>log msg</option>
<option value='author'>author</option>
<option value='committer'>committer</option>
<option value='range'>range</option>
</select>
<input class='txt' type='search' size='10' name='q' value=''/>
<input type='submit' value='search'/>
</form>
</td></tr></table>
<div class='path'>path: <a href='/guix/log/?id=ab9f9b582e510e3d1133ec29242e70fca1d2997a'>root</a>/<a href='/guix/log/gnu?id=ab9f9b582e510e3d1133ec29242e70fca1d2997a'>gnu</a>/<a href='/guix/log/gnu/packages?id=ab9f9b582e510e3d1133ec29242e70fca1d2997a'>packages</a>/<a href='/guix/log/gnu/packages/patches?id=ab9f9b582e510e3d1133ec29242e70fca1d2997a'>patches</a>/<a href='/guix/log/gnu/packages/patches/aegis-test-fixup-2.patch?id=ab9f9b582e510e3d1133ec29242e70fca1d2997a'>aegis-test-fixup-2.patch</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/packages/patches/aegis-test-fixup-2.patch?id=ab9f9b582e510e3d1133ec29242e70fca1d2997a&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>