gsoap: fix DEPENDS to prevent link failure for gsoap-native

With a fairly high number of threads I can reliably trigger the
following linker failure in gsoap-native:

| /usr/bin/ld: cannot find -ly
| collect2: error: ld returned 1 exit status
| Makefile:402: recipe for target 'soapcpp2' failed

Change the DEPENDS to include bison and let the BBCLASSEXTENDS
machinery fix DEPENDS for -native and -target variants, only
additonally adding gsoap-native to the DEPENDS for the target
recipe.

Signed-off-by: Joshua Lock <joshua.lock@collabora.co.uk>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>