testsuite: Unbreak T16608 tests

Sleep to avoid non-determinism due to Darwin's poor mtime resolution.
Fixes #16855.

testsuite/tests/driver/T16608/Makefile

@@ -5,6 +5,7 @@ include $(TOP)/mk/test.mk
 T16608_1:
 	'$(TEST_HC)' $(TEST_HC_OPTS) --make -O0 T16608_1.hs
 	./T16608_1
+	sleep 1
 	sed -i -e 's/{- . succ -}/. succ/' MyInteger.hs
 	'$(TEST_HC)' $(TEST_HC_OPTS) --make -O0 T16608_1.hs
 	./T16608_1
@@ -12,6 +13,7 @@ T16608_1:
 T16608_2:
 	'$(TEST_HC)' $(TEST_HC_OPTS) --make -O0 T16608_2.hs
 	./T16608_2
+	sleep 1
 	sed -i -e 's/{- . succ -}/. succ/' MyInteger.hs
 	'$(TEST_HC)' $(TEST_HC_OPTS) --make -O0 T16608_2.hs
 	./T16608_2

testsuite/tests/driver/T16608/all.T

-test('T16608_1', [when(opsys('darwin'), fragile(16855)), extra_files(['MyInteger.hs'])], makefile_test, [])
-test('T16608_2', [when(opsys('darwin'), fragile(16855)), extra_files(['MyInteger.hs'])], makefile_test, [])
+test('T16608_1', [extra_files(['MyInteger.hs'])], makefile_test, [])
+test('T16608_2', [extra_files(['MyInteger.hs'])], makefile_test, [])