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.old b/localedata/Makefile
index 34877c0..a61d9b9 100644
--- a/localedata/Makefile.old
+++ b/localedata/Makefile
@@ -91,7 +91,8 @@ endif
 # Files to install.
 install-others := $(addprefix $(inst_i18ndir)/, \
 			      $(addsuffix .gz, $(charmaps)) \
-			      $(locales))
+			      $(locales)) \
+                   $(inst_i18ndir)/SUPPORTED
 
 tests: $(objdir)/iconvdata/gconv-modules
 
@@ -195,6 +196,14 @@ 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 $@
+
 INSTALL-SUPPORTED-LOCALES=$(addprefix install-, $(SUPPORTED-LOCALES))
 
 # Sometimes the whole collection of locale files should be installed.
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<div class='path'>path: <a href='/guix/log/?id=d9f733ad8b8e782bae68869e742664458e0d68e6'>root</a>/<a href='/guix/log/gnu?id=d9f733ad8b8e782bae68869e742664458e0d68e6'>gnu</a>/<a href='/guix/log/gnu/packages?id=d9f733ad8b8e782bae68869e742664458e0d68e6'>packages</a>/<a href='/guix/log/gnu/packages/pcre.scm?id=d9f733ad8b8e782bae68869e742664458e0d68e6'>pcre.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/packages/pcre.scm?id=d9f733ad8b8e782bae68869e742664458e0d68e6&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2020-05-26 22:32:55 +0200'>2020-05-26</span></td><td><a href='/guix/commit/gnu/packages/pcre.scm?id=f2ff01bb8e794ead5d31548505c840caf6a9aa39'>gnu: pcre2: Update to 10.35.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/pcre.scm (pcre2): Update to 10.35.
</span></span></td><td>Marius Bakke</td></tr>
<tr><td><span title='2020-03-14 12:02:52 +0100'>2020-03-14</span></td><td><a href='/guix/commit/gnu/packages/pcre.scm?id=704f1b53c77f3550bc7b3e86aa7237db2fc1594e'>gnu: pcre: Update to 8.44.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/pcre.scm (pcre): Update to 8.44.
</span></span></td><td>Marius Bakke</td></tr>
<tr><td><span title='2019-12-11 23:21:55 +0100'>2019-12-11</span></td><td><a href='/guix/commit/gnu/packages/pcre.scm?id=f6943db7d39a060742b820e2f2f215b0bdeca690'>gnu: pcre2: Do not build static libraries.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/pcre.scm (pcre2)[arguments]: Add "--disable-static" to
 #:configure-flags.
</span></span></td><td>Marius Bakke</td></tr>
<tr><td><span title='2019-12-11 23:21:55 +0100'>2019-12-11</span></td><td><a href='/guix/commit/gnu/packages/pcre.scm?id=eccd2c14d6b42142e85ed517e8cfa81a73b6bd88'>gnu: pcre2: Update to 10.34.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/patches/pcre2-fix-jit_match-crash.patch: Delete file.
* gnu/local.mk (dist_patch_DATA): Adjust accordingly.
* gnu/packages/pcre.scm (pcre2): Update to 10.34.
[source](patches): Remove.
</span></span></td><td>Marius Bakke</td></tr>
<tr><td><span title='2019-08-13 20:42:06 +0200'>2019-08-13</span></td><td><a href='/guix/commit/gnu/packages/pcre.scm?id=462ad9f56b9665b8d22960acee73ad91f1052c9c'>Merge branch 'master' into core-updates</a></td><td>Marius Bakke</td></tr>
<tr><td><span title='2019-08-04 13:49:45 +0200'>2019-08-04</span></td><td><a href='/guix/commit/gnu/packages/pcre.scm?id=a33925d122c99eafb6e1e53ab1c122d7245d8a78'>gnu: Remove pcre2/fixed.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/pcre.scm (pcre2/fixed): Remove variable.
(pcre2)[replacement]: Remove.
[source](patches): New field.
* gnu/packages/php.scm (php)[inputs]: Change PCRE2/FIXED to PCRE2.
</span></span></td><td>Marius Bakke</td></tr>
<tr><td><span title='2019-08-02 01:49:47 +0200'>2019-08-02</span></td><td><a href='/guix/commit/gnu/packages/pcre.scm?id=951fd8572af1bd00064d5c0ae59c2927ec1b6ba5'>gnu: pcre@2: Fix run-time crash [security fix].</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/pcre.scm (pcre2)[replacement]: New field.
(pcre2/fixed): New public variable.
* packages/patches/pcre2-fix-jit_match-crash.patch: New file.
* gnu/local.mk (dist_patch_DATA): Add it.
</span></span></td><td>Tobias Geerinckx-Rice</td></tr>