build: Introduce introspection flags for Target

Using <target>.add_introspection_flag high level concepts can mark a
specific target in the introspection data.

mesonbuild/build.py

@@ -525,6 +525,7 @@ class Target(HoldableObject, metaclass=abc.ABCMeta):
     build_always_stale: bool = False
     extra_files: T.List[File] = field(default_factory=list)
     override_options: InitVar[T.Optional[T.Dict[OptionKey, str]]] = None
+    introspection_flags: T.Optional[T.List[str]] = None
 
     @abc.abstractproperty
     def typename(self) -> str:
@@ -637,6 +638,12 @@ def construct_id_from_path(subdir: str, name: str, type_suffix: str) -> str:
             return subdir_part + '@@' + my_id
         return my_id
 
+    def add_introspection_flag(self, flag: str) -> None:
+        if self.introspection_flags is None:
+            self.introspection_flags = [flag]
+        else:
+            self.introspection_flags.append(flag)
+
     def get_id(self) -> str:
         name = self.name
         if getattr(self, 'name_suffix_set', False):

mesonbuild/mintro.py

@@ -263,6 +263,9 @@ def list_targets(builddata: build.Build, installdata: backends.InstallData, back
             'depends': [lib.get_id() for lib in getattr(target, 'dependencies', [])]
         }
 
+        if target.introspection_flags:
+            t['flags'] = target.introspection_flags
+
         vs_module_defs = getattr(target, 'vs_module_defs', None)
         if vs_module_defs is not None:
             t['vs_module_defs'] = vs_module_defs.relative_name()

mesonbuild/modules/gnome.py

@@ -2222,6 +2222,7 @@ def executable(self, state: 'ModuleState', args: T.Tuple[str, SourcesVarargsType
                 target = state.add_target(args, kwargs, build.SharedLibrary)
             glue = state.dependency('gtk4-android-glue')
             target.add_deps([glue])
+            target.add_introspection_flag('gnome:has-android-glue')
         else:
             target = state.add_target(args, kwargs, build.Executable)
         return ModuleReturnValue(target, [])