cairo is always required

the meson build script for gtk3 has:
- cairo_dep      = dependency('cairo', version: cairo_req, required: cc.get_id() != 'msvc')
that is cairo is not required if msvc, but this is because they use
another search criteria right after for windows
- if not cairo_dep.found() and cc.get_id() == 'msvc'
-   if cc.has_header('cairo.h') and cc.has_header('cairo-win32.h')
-     cairo_dep = cc.find_library('cairo', required: false)
-   endif
- endif
-
- if not cairo_dep.found()
-   cairo_dep      = dependency('cairo', version: cairo_req,
-                               fallback : ['cairo', 'libcairo_dep'])
- endif
and eventually cairo has to be found for gtk to be built

recipes/gtk/all/conanfile.py

@@ -124,8 +124,7 @@ def build_requirements(self):
     def requirements(self):
         self.requires("gdk-pixbuf/2.42.8")
         self.requires("glib/2.73.0")
-        if self._gtk4 or self.settings.compiler != "Visual Studio":
-            self.requires("cairo/1.17.4")
+        self.requires("cairo/1.17.4")
         if self._gtk4:
             self.requires("graphene/1.10.8")
             self.requires("fribidi/1.0.12")