[at-spi2-core] meson: Specify version when defining _POSIX_C_SOURCE

[Mike Gorse <mgorse src gnome org>]

commit ef43d25c9ff499f14a9a7fa24ce2ac779fa52ae5
Author: Ting-Wei Lan <lantw src gnome org>
Date:   Thu Dec 14 20:11:21 2017 +0800

    meson: Specify version when defining _POSIX_C_SOURCE
    
    FreeBSD libc assumes defining _POSIX_C_SOURCE without specifying a
    version means a pre-C89 environment with the oldest version of POSIX
    standard, IEEE Std 1003.1-1988, causing va_copy in C99 to be hidden.
    To resolve this problem, simply provide a version number when
    defining _POSIX_C_SOURCE.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=791608

 meson.build |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/meson.build b/meson.build
index dbacc0d..aaa0f72 100644
--- a/meson.build
+++ b/meson.build
@@ -8,7 +8,7 @@ project('at-spi2-core', 'c',
         ],
         meson_version: '>= 0.40.1')
 
-add_project_arguments([ '-D_POSIX_C_SOURCE', '-D_DEFAULT_SOURCE' ], language: 'c')
+add_project_arguments([ '-D_POSIX_C_SOURCE=200809L', '-D_DEFAULT_SOURCE' ], language: 'c')
 
 atspi_gir_ns = 'Atspi'