add assimp package. link against it in dealii (#5463)

var/spack/repos/builtin/packages/dealii/package.py

@@ -49,6 +49,8 @@ class Dealii(CMakePackage):
     version('develop', git='https://github.com/dealii/dealii.git', branch='master')
 
     variant('mpi',      default=True,  description='Compile with MPI')
+    variant('assimp',   default=False,
+            description='Compile with Assimp')
     variant('arpack',   default=True,
             description='Compile with Arpack and PArpack (only with MPI)')
     variant('adol-c',   default=False,
@@ -121,6 +123,7 @@ class Dealii(CMakePackage):
     depends_on("mpi",              when="+mpi")
     depends_on("adol-c@2.6.4:",    when='@9.0:+adol-c')
     depends_on("arpack-ng+mpi",    when='+arpack+mpi')
+    depends_on("assimp",           when='@9.0:+assimp')
     depends_on("doxygen+graphviz", when='+doc')
     depends_on("graphviz",         when='+doc')
     depends_on("gsl",              when='@8.5.0:+gsl')
@@ -148,6 +151,7 @@ class Dealii(CMakePackage):
     depends_on("trilinos+amesos+aztec+epetra+ifpack+ml+muelu+sacado+teuchos~hypre", when="+trilinos+mpi+int64")
 
     # check that the combination of variants makes sense
+    conflicts('+assimp', when='@:8.5.1')
     conflicts('+nanoflann', when='@:8.5.1')
     conflicts('+sundials', when='@:8.5.1')
     conflicts('+adol-c', when='@:8.5.1')
@@ -286,6 +290,17 @@ def cmake_args(self):
                 '-DDEAL_II_WITH_ARPACK=OFF'
             ])
 
+        # Assimp
+        if '+assimp' in spec:
+            options.extend([
+                '-DEAL_II_WITH_ASSIMP=ON',
+                '-DASSIMP_DIR=%s' % spec['assimp'].prefix
+            ])
+        else:
+            options.extend([
+                '-DEAL_II_WITH_ASSIMP=OFF'
+            ])
+
         # since Netcdf is spread among two, need to do it by hand:
         if '+netcdf' in spec and '+mpi' in spec:
             # take care of lib64 vs lib installed lib locations: