modules/gnome: Fix handling of flags to genmarshal

These are actually just flags, they don't take any arguments (except
prefix, which was already handled correctly), and as such their
arguments should be booleans, not strings, and they should default to
False.

mesonbuild/modules/gnome.py

@@ -148,13 +148,13 @@ if T.TYPE_CHECKING:
         extra_args: T.List[str]
         install_dir: T.List[T.Union[str, bool]]
         install_header: bool
-        internal: T.Optional[str]
-        nostdinc: T.Optional[str]
+        internal: bool
+        nostdinc: bool
         prefix: T.Optional[str]
-        skip_source: T.Optional[str]
+        skip_source: bool
         sources: T.List[str]
-        stdinc: T.Optional[str]
-        valist_marshallers: T.Optional[str]
+        stdinc: bool
+        valist_marshallers: bool
 
     class GenerateVapi(TypedDict):
 
@@ -1728,13 +1728,13 @@ class GnomeModule(ExtensionModule):
         INSTALL_KW.evolve(name='install_header'),
         KwargInfo('extra_args', ContainerTypeInfo(list, str), listify=True, default=[]),
         KwargInfo('install_dir', (str, NoneType)),
-        KwargInfo('internal', (str, NoneType)),
-        KwargInfo('nostdinc', (str, NoneType)),
+        KwargInfo('internal', bool, default=False),
+        KwargInfo('nostdinc', bool, default=False),
         KwargInfo('prefix', (str, NoneType)),
-        KwargInfo('skip_source', (str, NoneType)),
+        KwargInfo('skip_source', bool, default=False),
         KwargInfo('sources', ContainerTypeInfo(list, str, allow_empty=False), listify=True, required=True),
-        KwargInfo('stdinc', (str, NoneType)),
-        KwargInfo('valist_marshallers', (str, NoneType)),
+        KwargInfo('stdinc', bool, default=False),
+        KwargInfo('valist_marshallers', bool, default=False),
     )
     def genmarshal(self, state: 'ModuleState', args: T.Tuple[str], kwargs: 'GenMarshal') -> ModuleReturnValue:
         output = args[0]
@@ -1755,7 +1755,7 @@ class GnomeModule(ExtensionModule):
         for k in ['internal', 'nostdinc', 'skip_source', 'stdinc', 'valist_marshallers']:
             # Mypy can't figure out that this is correct
             if kwargs[k]:                                            # type: ignore
-                cmd.extend([f'--{k.replace("_", "-")}', kwargs[k]])  # type: ignore
+                cmd.append(f'--{k.replace("_", "-")}')
 
         install_header = kwargs['install_header']
         install_dir = kwargs['install_dir']