cyrus-sasl: add login PACKAGECONFIG

The LOGIN mechanism is disabled by default in the configure script,
so libsasl2 clients fail with "no mechanism available" as soon as a
peer only offers AUTH LOGIN or the client is configured to use it.
Mail servers still commonly advertise AUTH LOGIN PLAIN and clients like
KMail default to LOGIN for SMTP transports. Debian, Fedora and Gentoo
all ship the plugin.

Add an opt-in PACKAGECONFIG that builds liblogin.so, off by default to
keep the current behaviour.

Tested on corei7-64 with the option enabled, liblogin.so is packaged
into ${libdir}/sasl2 next to the other mechanism plugins.

AI-Generated: Uses Claude Code (Claude Fable 5.1)
Signed-off-by: Markus Volk <f_l_k@t-online.de>
Signed-off-by: Khem Raj <khem.raj@oss.qualcomm.com>

meta-oe/recipes-networking/cyrus-sasl/cyrus-sasl_2.1.28.bb

@@ -41,6 +41,7 @@ PACKAGECONFIG[opie] = "--with-opie,--without-opie,opie,"
 PACKAGECONFIG[des] = "--with-des,--without-des,,"
 PACKAGECONFIG[ldap] = "--with-ldap=${STAGING_LIBDIR} --enable-ldapdb,--without-ldap --disable-ldapdb,openldap,"
 PACKAGECONFIG[ntlm] = "--enable-ntlm=yes,--enable-ntlm=no,,"
+PACKAGECONFIG[login] = "--enable-login,--disable-login,,"
 
 CFLAGS += "-fPIC"