Modify cgroup tests to make the tests pass with the new behavior.

The cgroups mounting is changed, in the root container cgroups are mounted
by default and for other containers the cgroups are mounted if the spec has a
cgroup mount. These tests mount cgroups directly which will fail. This CL
modifies the cgroup tests to pass with the new behavior.

PiperOrigin-RevId: 596739547

test/runner/main.go

@@ -651,6 +651,11 @@ func runTestCaseRunsc(testBin string, tc *gtest.TestCase, args []string, t *test
 		defer cleanup()
 	}
 
+	// Add cgroup mount to enable cgroups for all tests.
+	spec.Mounts = append(spec.Mounts, specs.Mount{
+		Destination: "/sys/fs/cgroup",
+		Type:        "cgroup",
+	})
 	if err := runRunsc(tc, spec); err != nil {
 		t.Errorf("test %q failed with error %v, want nil", tc.FullName(), err)
 	}

test/syscalls/BUILD

@@ -64,14 +64,10 @@ syscall_test(
     test = "//test/syscalls/linux:brk_test",
 )
 
-# TODO(b/315355651): Fix cgroup tests in runsc. Cgroups are mounted in the
-# root/pause container by default and for other containers cgroups are bind
-# mounted if the container spec has a cgroup mount. These cgroup tests
-# explicitly mount the cgroups which will fail now in runsc.
-# syscall_test(
-#     one_sandbox = False,
-#     test = "//test/syscalls/linux:cgroup_test",
-# )
+syscall_test(
+    one_sandbox = False,
+    test = "//test/syscalls/linux:cgroup_test",
+)
 
 syscall_test(
     add_fusefs = True,

test/syscalls/linux/BUILD

@@ -4576,6 +4576,7 @@ cc_binary(
         "//test/util:mount_util",
         "@com_google_absl//absl/strings",
         "@com_google_absl//absl/synchronization",
+        "@com_google_absl//absl/time",
         gtest,
         "//test/util:cleanup",
         "//test/util:posix_error",