trilinos: allow to compile exodus (#3857)

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

@@ -86,6 +86,7 @@ class Trilinos(CMakePackage):
     variant('debug',        default=False,
             description='Builds a debug version of the libraries')
     variant('boost',        default=True, description='Compile with Boost')
+    variant('exodus', default=False, description='Compile with Exodus from SEACAS')
 
     # Everything should be compiled with -fpic
     depends_on('blas')
@@ -371,11 +372,20 @@ def cmake_args(self):
 
         # disable due to compiler / config errors:
         options.extend([
-            '-DTrilinos_ENABLE_SEACAS=OFF',
             '-DTrilinos_ENABLE_Pike=OFF',
             '-DTrilinos_ENABLE_STK=OFF'
         ])
 
+        # exodus
+        if '+exodus' in spec:
+            options.extend([
+                '-DTrilinos_ENABLE_SEACAS:BOOL=ON'
+            ])
+        else:
+            options.extend([
+                '-DTrilinos_ENABLE_SEACAS:BOOL=OFF'
+            ])
+ 
         # disable due to compiler / config errors:
         if spec.satisfies('%xl') or spec.satisfies('%xl_r'):
             options.extend([