testsuite: Eliminate fragility of ioprof

As noted in #10037, the `ioprof` test would change its stderr output
(specifically the stacktrace produced by `error`) depending upon
optimisation level. As the `error` backtrace is not the point of this
test, we now ignore the `stderr` output.

testsuite/tests/profiling/should_run/all.T

@@ -92,7 +92,8 @@ test('T949', [extra_ways(extra_prof_ways)], compile_and_run, [''])
 test('ioprof',
      [expect_broken_for_10037,
       exit_code(1),
-      omit_ways(['ghci-ext-prof']) # doesn't work with exit_code(1)
+      omit_ways(['ghci-ext-prof']), # doesn't work with exit_code(1)
+      ignore_stderr
      ],
      compile_and_run,
      ['-fno-full-laziness -fno-state-hack']) # Note [consistent stacks]

testsuite/tests/profiling/should_run/ioprof.stderr

-ioprof: a
-CallStack (from HasCallStack):
-  error, called at ioprof.hs:23:22 in main:Main
-CallStack (from -prof):
-  Main.errorM.\ (ioprof.hs:23:22-28)
-  Main.errorM (ioprof.hs:23:1-28)
-  Main.foo (ioprof.hs:34:1-16)
-  Main.>>=.\ (ioprof.hs:(11,27)-(12,50))
-  Main.>>= (ioprof.hs:(11,3)-(12,50))
-  Main.<*> (ioprof.hs:20:5-14)
-  Main.bar (ioprof.hs:31:1-20)
-  Main.runM (ioprof.hs:26:1-37)
-  Main.main (ioprof.hs:28:1-43)