Julian Lettner 0ffe848c65 [lit] Allow setting parallelism groups to None ...

Check that we do not crash if a parallelism group is explicitly set to
None. Permits usage of the following pattern.

[lit.common.cfg]
  lit_config.parallelism_groups['my_group'] = None
  if <condition>:
    lit_config.parallelism_groups['my_group'] = 3

[project/lit.cfg]
  config.parallelism_group = 'my_group'

Reviewers: rnk

Differential Revision: https://reviews.llvm.org/D58305

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@354912 91177308-0d34-0410-b5e6-96231b3b80d8

2019-02-26 19:03:26 +00:00

..

lit.cfg

…

test1.txt

…

test2.txt

…