testsuite: Add testcase for #8316

This is still broken but really out to be fixed. At least know we'll
know if someone fixes it inadvertently.

Test Plan: validate

Reviewers: austin

Reviewed By: austin

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D1682

GHC Trac Issues: #8316

testsuite/tests/ghci/scripts/T8316.hs

+whnf :: a -> IO ()
+whnf a = a `seq` (return ())
+
+foo :: [Int]
+foo = [1..]

testsuite/tests/ghci/scripts/T8316.script

+:b foo
+foo
+:p foo
+whnf _t1
\ No newline at end of file

testsuite/tests/ghci/scripts/all.T

@@ -231,3 +231,4 @@ test('T10989',
     ],
     ghci_script, ['T10989.script'])
 test('T11098', normal, ghci_script, ['T11098.script'])
+test('T8316', expect_broken(8316), ghci_script, ['T8316.script'])