Mark T11978a as broken due to #12019

Test Plan: `validate --slow`

Reviewers: austin

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2536

GHC Trac Issues: #12019

testsuite/tests/profiling/should_run/all.T

@@ -110,7 +110,9 @@ test('T11627b', [ extra_run_opts('+RTS -i0 -RTS')  # census after each GC
                 , [''])
 
 test('T11978a',
-     [only_ways(['profthreaded']), extra_run_opts('+RTS -hb -N10')],
+     [only_ways(['profthreaded']),
+      extra_run_opts('+RTS -hb -N10'),
+      expect_broken(12019)],
      compile_and_run, [''])
 
 test('toplevel_scc_1',