[newlib-cygwin] cygwin: fix getconf after commit 032aa2dba5a5bf90c198d930c8d309b5de57cb47

[Yaakov Selkowitz]

https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=c37171b528502aad4b55d329ff91a55335b641ad

commit c37171b528502aad4b55d329ff91a55335b641ad
Author: Yaakov Selkowitz <yselkowi@redhat.com>
Date:   Tue Nov 28 11:35:13 2017 -0600

    cygwin: fix getconf after commit 032aa2dba5a5bf90c198d930c8d309b5de57cb47
    
    Signed-off-by: Yaakov Selkowitz <yselkowi@redhat.com>

Diff:
---
 winsup/utils/getconf.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/winsup/utils/getconf.c b/winsup/utils/getconf.c
index e6b319e..256bddb 100644
--- a/winsup/utils/getconf.c
+++ b/winsup/utils/getconf.c
@@ -27,6 +27,7 @@
  * POSSIBILITY OF SUCH DAMAGE.
  */
 
+#define _XOPEN_SOURCE
 #include <error.h>
 #include <errno.h>
 #include <limits.h>