src/sage/features/sagemath.py: mark sage.libs.giac as optional

Author: orlitzky

src/sage/features/sagemath.py

@@ -560,7 +560,7 @@ def __init__(self):
         """
         JoinFeature.__init__(self, 'sage.libs.giac',
                              [PythonModule('sage.libs.giac.giac')],
-                             spkg='sagemath_giac', type='standard')
+                             spkg='sagemath_giac', type='optional')
 
 
 class sage__libs__homfly(JoinFeature):