tests: Assert that mips64 kernel is detected as mips64 with no compilers

Reproduces: https://github.com/mesonbuild/meson/issues/12017
Signed-off-by: Simon McVittie <smcv@debian.org>

unittests/internaltests.py

@@ -1600,6 +1600,16 @@ class InternalTests(unittest.TestCase):
                     actual = mesonbuild.environment.detect_cpu_family({'c': cc})
                     self.assertEqual(actual, expected)
 
+        # machine_info_can_run calls detect_cpu_family with no compilers at all
+        with mock.patch(
+            'mesonbuild.environment.any_compiler_has_define',
+            mock.Mock(side_effect=AssertionError('Should not be called')),
+        ):
+            for test, expected in [('mips64', 'mips64')]:
+                with self.subTest(test, has_compiler=False), mock_trial(test):
+                    actual = mesonbuild.environment.detect_cpu_family({})
+                    self.assertEqual(actual, expected)
+
     def test_detect_cpu(self) -> None:
 
         @contextlib.contextmanager
@@ -1639,6 +1649,15 @@ class InternalTests(unittest.TestCase):
                     actual = mesonbuild.environment.detect_cpu({'c': cc})
                     self.assertEqual(actual, expected)
 
+        with mock.patch(
+            'mesonbuild.environment.any_compiler_has_define',
+            mock.Mock(side_effect=AssertionError('Should not be called')),
+        ):
+            for test, expected in [('mips64', 'mips64')]:
+                with self.subTest(test, has_compiler=False), mock_trial(test):
+                    actual = mesonbuild.environment.detect_cpu({})
+                    self.assertEqual(actual, expected)
+
     def test_interpreter_unpicklable(self) -> None:
         build = mock.Mock()
         build.environment = mock.Mock()