nest: fix failing build of `nest~mpi`

packages/nest/package.py

@@ -93,7 +93,7 @@ class Nest(CMakePackage):
     depends_on('boost',             when="@2.16:+boost", type='build')
     depends_on('py-setuptools@:44.99.99',     when='@:2.15.99+python', type='build')
     depends_on('py-h5py',           when='@3.4.99:+sonata', type=('test', 'build', 'run'))
-    depends_on('hdf5+cxx',          when='@3.4.99:+sonata', type=('build', 'run'))
+    depends_on('hdf5+cxx',          when='@3.4.99:+sonata', type=('build', 'link', 'run'))
     depends_on('py-pandas',         when='@3.4.99:+sonata', type=('build', 'run'))
 
     depends_on('py-nose',           when='@:2.99.99+python+testsuite', type='test')
@@ -149,7 +149,7 @@ class Nest(CMakePackage):
         else:
             configure_args.append("--without-optimize")
 
-        if 'mpi' in spec:
+        if '+mpi' in spec:
             env['CC'] = spec['mpi'].mpicc
             env['CXX'] = spec['mpi'].mpicxx
             env['F77'] = spec['mpi'].mpif77