gnome: support using generate_gir from gobject-introspection

From gobject-introspection itself the use of gnome.generate_gir is
not possible leading to several hacks that are hard to maintain in
order to support building gobject-introspection with submodules.

This change in combination with https://gitlab.gnome.org/GNOME/gobject-introspection/-/merge_requests/380
uses a new `gobject-introspection-no-typelibs` dependency to allow
defining dependency to allow using the GI dependency prior to having
the typelibs generated.

mesonbuild/modules/gnome.py

@@ -789,10 +789,13 @@ def get_devenv(self) -> T.Optional[build.EnvironmentVariables]:
 
     def _get_gir_dep(self, state: 'ModuleState') -> T.Tuple[Dependency, T.Union[build.Executable, 'ExternalProgram', 'OverrideProgram'],
                                                             T.Union[build.Executable, 'ExternalProgram', 'OverrideProgram']]:
-        if not self.gir_dep:
-            self.gir_dep = state.dependency('gobject-introspection-1.0')
-            self.giscanner = state.find_tool('g-ir-scanner', 'gobject-introspection-1.0', 'g_ir_scanner')
-            self.gicompiler = state.find_tool('g-ir-compiler', 'gobject-introspection-1.0', 'g_ir_compiler')
+        if not self.gir_dep or not self.gir_dep.found():
+            for (dep, req) in [('gobject-introspection-no-typelibs-1.0', False), ('gobject-introspection-1.0', True)]:
+                self.gir_dep = state.dependency(dep, required=req)
+                self.giscanner = state.find_tool('g-ir-scanner', dep, 'g_ir_scanner', required=req)
+                self.gicompiler = state.find_tool('g-ir-compiler', dep, 'g_ir_compiler', required=req)
+                if self.gir_dep.found():
+                    break
         return self.gir_dep, self.giscanner, self.gicompiler
 
     @functools.lru_cache(maxsize=None)