unix_chkpwd is designed to have a suid bit, but it's not possible to set it
for files in the store.  This patch tells unix_pam.so to look for
unix_chkpwd in setuid program directory on Guix System.

--- a/modules/pam_unix/Makefile.in
+++ b/modules/pam_unix/Makefile.in
@@ -651,1 +651,1 @@
-	-DCHKPWD_HELPER=\"$(sbindir)/unix_chkpwd\" \
+	-DCHKPWD_HELPER=\"/run/setuid-programs/unix_chkpwd\" \
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<tr><td><span title='2021-01-14 16:20:45 +0100'>2021-01-14</span></td><td><a href='/guix/commit/gnu/packages/text-editors.scm?id=f5c9e76f97d426f081b45328fdb70aaa757a284b'>gnu: jucipp: Update to 1.6.2.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/text-editors.scm (jucipp): Update to 1.6.2.
</span></span></td><td>Tobias Geerinckx-Rice</td></tr>