Fix #9642 - fdopen(3) requires _POSIX_C_SOURCE

Without this, fdopen() returns some garbage FILE* which
causes a crash when used.

libs/tk/ydk-pixbuf/wscript

@@ -1,6 +1,7 @@
 #!/usr/bin/env python
 from waflib.extras import autowaf as autowaf
 import sys
+import re
 
 # Version of this package (even if built as a child)
 MAJOR = '2'
@@ -63,3 +64,6 @@ def build(bld):
     if sys.platform == 'darwin':
         obj.uselib     += ' OSX'
         obj.ldflags     = ' -lintl'
+
+    if re.search ("bsd", sys.platform) != None:
+        obj.defines.append('_POSIX_C_SOURCE=200809')