[glib: 1/2] Set G_WITH_CYGWIN again

[Philip Withnall <pwithnall src gnome org>]

commit 9ca7ac782e9f8cc8d4648d45afd39d0ab7ef7289
Author: Руслан Ижбулатов <lrn1986 gmail com>
Date:   Wed Mar 20 19:05:19 2019 +0000

    Set G_WITH_CYGWIN again
    
    This macro was lost during meson migration. Set it again.
    
    Also explain that Cygwin maintainers applied patches[0] to glib that
    simply marked all G_PLATFORM_WIN32-protected code as !defined(G_WITH_CYGWIN),
    i.e. they did not want that code to compile.
    Instead of altering ifdef guards all over the place, we'll just
    not define G_PLATFORM_WIN32 for Cygwin anymore.
    
    [0]: 
https://github.com/cygwinports/glib2.0/blob/3a873fdd1b9a9e649563fe8e6b8ae6951b0dd3be/2.36.3-not-win32.patch

 meson.build | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)
---
diff --git a/meson.build b/meson.build
index d937b5fa3..9622ced5c 100644
--- a/meson.build
+++ b/meson.build
@@ -188,10 +188,18 @@ if host_system == 'windows' and get_option('default_library') == 'static'
     glibconfig_conf.set('GOBJECT_STATIC_COMPILATION', '1')
 endif
 
-# FIXME: what about Cygwin (G_WITH_CYGWIN)
+# Cygwin glib port maintainers made it clear
+# (via the patches they apply) that they want no
+# part of glib W32 code, therefore we do not define
+# G_PLATFORM_WIN32 for host_system == 'cygwin'.
+# This makes G_PLATFORM_WIN32 a synonym for
+# G_OS_WIN32.
 if host_system == 'windows'
   glib_os = '''#define G_OS_WIN32
 #define G_PLATFORM_WIN32'''
+elif host_system == 'cygwin'
+  glib_os = '''#define G_OS_WIN32
+#define G_WITH_CYGWIN'''
 else
   glib_os = '#define G_OS_UNIX'
 endif