package/unbound: select BR2_PACKAGE_LIBOPENSSL_ENGINES

unbound unconditionally calls the (deprecated) ENGINE_* logic in
libopenssl resulting in a build failure when
!BR2_PACKAGE_LIBOPENSSL_ENGINES since commit
623d3bbe43e9193aa8e3395367d01af59071b859:

sldns/keyraw.c:167:35: error: 'ENGINE_METHOD_ALL' undeclared (first use in this function)
  167 |         if(!ENGINE_set_default(e, ENGINE_METHOD_ALL)) {
      |                                   ^~~~~~~~~~~~~~~~~

Fixes: 623d3bbe43e9193aa8e3395367d01af59071b859
 - http://autobuild.buildroot.org/results/b7782f5ba54543df53a835552632f58d4ad6c082

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
(cherry picked from commit ec7ae882e048ce4ca5c2b72cb884b8d1ef33c6cc)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/unbound/Config.in

@@ -3,6 +3,7 @@ config BR2_PACKAGE_UNBOUND
 	depends on !BR2_STATIC_LIBS
 	select BR2_PACKAGE_EXPAT
 	select BR2_PACKAGE_LIBEVENT
+	select BR2_PACKAGE_LIBOPENSSL_ENGINES if BR2_PACKAGE_LIBOPENSSL
 	select BR2_PACKAGE_OPENSSL
 	help
 	  Unbound is a validating, recursive, and caching DNS resolver.