build: Fix MSVC warning due to Pango bug

Pango unconditionally defines STRICT, which we use, see
https://learn.microsoft.com/en-us/windows/win32/winprog/enabling-strict

And that causes a duplicate definition, so we undefined it before
including the offending Pango header.

See also https://gitlab.gnome.org/GNOME/pango/-/merge_requests/749

gsk/gskrendernodeparser.c

@@ -56,6 +56,7 @@
 #include <pango/pangofc-fontmap.h>
 #endif
 #ifdef HAVE_PANGOWIN32
+#undef STRICT
 #include <pango/pangowin32.h>
 #endif