fix(jaxsnn): Provide genpybind via build-brainscales

This is somewhat ugly, we should rather introduce a list of dependencies
that are requires for building `hxtorch.core` (which is build by both,
`hxtorch` and `jaxsnn`) and use it in jaxsnn.

packages/build-brainscales/package.py

@@ -18,6 +18,9 @@ class BuildBrainscales(WafPackage):
     depends_on('git', type=('build', 'link'))
     depends_on('py-git-review', type=('build', 'link'))
 
+    # hack to provide genpybind PATH in all brainscales-style builds
+    depends_on('genpybind@ebrains', type=('build', 'link'))
+
     def do_fetch(self, mirror_only=False):
         """Setup the project."""