interpreter: disallow RunTarget in test

Fixes the following error in the testcase:

  File "/usr/lib/python3.10/site-packages/mesonbuild/backend/ninjabackend.py", line 548, in generate
    self.generate_tests()
  File "/usr/lib/python3.10/site-packages/mesonbuild/backend/ninjabackend.py", line 1093, in generate_tests
    self.serialize_tests()
  File "/usr/lib/python3.10/site-packages/mesonbuild/backend/backends.py", line 567, in serialize_tests
    self.write_test_file(datafile)
  File "/usr/lib/python3.10/site-packages/mesonbuild/backend/backends.py", line 943, in write_test_file
    self.write_test_serialisation(self.build.get_tests(), datafile)
  File "/usr/lib/python3.10/site-packages/mesonbuild/backend/backends.py", line 1017, in write_test_serialisation
    pickle.dump(self.create_test_serialisation(tests), datafile)
  File "/usr/lib/python3.10/site-packages/mesonbuild/backend/backends.py", line 1002, in create_test_serialisation
    cmd_args.append(self.construct_target_rel_path(a, t.workdir))
  File "/usr/lib/python3.10/site-packages/mesonbuild/backend/backends.py", line 1021, in construct_target_rel_path
    return self.get_target_filename(a)
  File "/usr/lib/python3.10/site-packages/mesonbuild/backend/backends.py", line 253, in get_target_filename
    assert(isinstance(t, build.BuildTarget))

mesonbuild/interpreter/interpreter.py

@@ -192,7 +192,7 @@ known_build_target_kwargs = (
 )
 
 TEST_KWARGS: T.List[KwargInfo] = [
-    KwargInfo('args', ContainerTypeInfo(list, (str, mesonlib.File, build.Target)),
+    KwargInfo('args', ContainerTypeInfo(list, (str, mesonlib.File, build.BuildTarget, build.CustomTarget)),
               listify=True, default=[]),
     KwargInfo('should_fail', bool, default=False),
     KwargInfo('timeout', int, default=30),

test cases/failing/116 run_target in test/meson.build

@@ -0,0 +1,4 @@
+project('trivial test', 'c')
+exe = executable('trivialprog', 'trivial.c')
+runt = run_target('invalid', command: ['echo', 'run_target'])
+test('runtest', exe, args: runt)

test cases/failing/116 run_target in test/test.json

@@ -0,0 +1,8 @@
+{
+    "stdout": [
+        {
+            "line": "test cases/failing/116 run_target in test/meson.build:4:0: ERROR: test keyword argument 'args' was of type 'list' but should have been list[str,File,BuildTarget,CustomTarget]"
+        }
+    ]
+}
+

test cases/failing/116 run_target in test/trivial.c

@@ -0,0 +1,6 @@
+#include<stdio.h>
+
+int main(void) {
+    printf("Trivial test is working.\n");
+    return 0;
+}