build: make sure _GNU_SOURCE is set

Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

diff --git a/configure.ac b/configure.ac
index 1c579d2dcc4d72ff8f6708aaeff4800da6d06282..df2d8a5d436cc7d5f01ec30d1905dccd489512a8 100644 (file)
--- a/configure.ac
+++ b/configure.ac
@@ -44,6 +44,7 @@ AC_CANONICAL_HOST
 AM_PROG_CC_C_O
 AC_USE_SYSTEM_EXTENSIONS
 AC_SYS_LARGEFILE
+AC_GNU_SOURCE
 
 # Test if we have a new enough compiler.
 AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[