[gegl] meson: force support for 64bit file offsets on win32

[Øyvind "pippin" Kolås <ok src gnome org>]

commit b2c2425bbb5b5501ecfe12bec7a6432d819e3b60
Author: Øyvind Kolås <pippin gimp org>
Date:   Sat Mar 21 13:29:13 2020 +0100

    meson: force support for 64bit file offsets on win32
    
    Fallout from autotools->meson port, where we lost ability to use more
    than 2GB of swap on 32 bit windows.
    
    This might not be neccesary in the future, if meson starts defining this
    for windows itself https://github.com/mesonbuild/meson/pull/1455
    
    Fixes issue #231

 meson.build | 4 ++++
 1 file changed, 4 insertions(+)
---
diff --git a/meson.build b/meson.build
index 4b6a7dfca..70c598d19 100644
--- a/meson.build
+++ b/meson.build
@@ -118,6 +118,10 @@ cflags_c = [
   '-Wold-style-definition',
 ]
 
+if os_win32
+  cflags_common += [ '-D_FILE_OFFSET_BITS=64' ]
+endif
+
 cflags_c   = cflags_common + cflags_c
 cflags_cpp = cflags_common + cflags_cpp