hash-object: add another >4GB/LLP64 test case

To complement the `--stdin` and `--literally` test cases that verify
that we can hash files larger than 4GB on 64-bit platforms using the
LLP64 data model, here is a test case that exercises `hash-object`
_without_ any options.

Just as before, we use the `big` file from the previous test case if it
exists to save on setup time, otherwise generate it.

Signed-off-by: Philip Oakley <philipoakley@iee.email>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

t/t1007-hash-object.sh

@@ -268,4 +268,12 @@ test_expect_success EXPENSIVE,SIZE_T_IS_64BIT,!LONG_IS_64BIT \
 	test_cmp expect actual
 '
 
+test_expect_success EXPENSIVE,SIZE_T_IS_64BIT,!LONG_IS_64BIT \
+		'files over 4GB hash correctly' '
+	{ test -f big || test-tool genzeros $((5*1024*1024*1024)) >big; } &&
+	test_oid large5GB >expect &&
+	git hash-object -- big >actual &&
+	test_cmp expect actual
+'
+
 test_done