remove default separate_build_dir = True in opencv.py

Author: branfosj

easybuild/easyblocks/o/opencv.py

@@ -53,7 +53,6 @@ def extra_options():
         extra_vars.update({
             'cpu_dispatch': ['NONE', "Value to pass to -DCPU_DISPATCH configuration option", CUSTOM],
         })
-        extra_vars['separate_build_dir'][0] = True
         return extra_vars
 
     def __init__(self, *args, **kwargs):