[gtk+] build: Use the appropriate symbol visibility annotation

[Emmanuele Bassi <ebassi src gnome org>]

commit e3f99fa2df0ef52f3624159e19d2828552a8a1c5
Author: Emmanuele Bassi <ebassi gnome org>
Date:   Tue Aug 22 10:27:14 2017 +0100

    build: Use the appropriate symbol visibility annotation
    
    We cargo-culted this from Autotools, but GCC on Windows supports the
    same __declspec syntax as MSVC. The only difference is the additional
    flag needed for GCC-like compilers.

 meson.build |    6 ++----
 1 files changed, 2 insertions(+), 4 deletions(-)
---
diff --git a/meson.build b/meson.build
index 158e5c8..52a0807 100644
--- a/meson.build
+++ b/meson.build
@@ -279,10 +279,8 @@ endforeach
 if get_option('default_library') != 'static'
   if host_machine.system() == 'windows'
     cdata.set('DLL_EXPORT', true)
-    if cc.get_id() == 'msvc'
-      cdata.set('_GDK_EXTERN', '__declspec(dllexport) extern')
-    else
-      cdata.set('_GDK_EXTERN', '__attribute__((visibility("default"))) __declspec(dllexport) extern')
+    cdata.set('_GDK_EXTERN', '__declspec(dllexport) extern')
+    if cc.get_id() != 'msvc'
       common_cflags += ['-fvisibility=hidden']
     endif
   else