package/msmtp: prefer gnutls over openssl

Msmtp no longer uses openssl as default [1], and even discourages the
use of the OpenSSL. Let's follow this upstream recommendation: if the
Buildroot configuration has both OpenSSL and GnuTLS enabled, GnuTLS
will be preferred over OpenSSL.

[1] https://marlam.de/msmtp/news/openssl-discouraged/

Signed-off-by: Ryan Coe <bluemrp9@gmail.com>
[Thomas: improve commit log]
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

package/msmtp/msmtp.mk

@@ -40,16 +40,16 @@ else
 MSMTP_CONF_OPTS += --without-libsecret
 endif
 
-ifeq ($(BR2_PACKAGE_OPENSSL),y)
+ifeq ($(BR2_PACKAGE_GNUTLS),y)
+MSMTP_CONF_OPTS += --with-tls=gnutls
+MSMTP_DEPENDENCIES += gnutls
+else ifeq ($(BR2_PACKAGE_OPENSSL),y)
 MSMTP_CONF_OPTS += --with-tls=openssl
 MSMTP_DEPENDENCIES += openssl
 ifeq ($(BR2_STATIC_LIBS),y)
 # openssl uses zlib, so we need to explicitly link with it when static
 MSMTP_CONF_ENV += LIBS=-lz
 endif
-else ifeq ($(BR2_PACKAGE_GNUTLS),y)
-MSMTP_CONF_OPTS += --with-tls=gnutls
-MSMTP_DEPENDENCIES += gnutls
 else
 MSMTP_CONF_OPTS += --with-tls=no
 endif