configure: Add _GNU_SOURCE to strlcpy configure test

>=glibc-2.38 adds strlcpy but it's guarded under a feature-test macro. Just
add _GNU_SOURCE to the configure test because we already pass _GNU_SOURCE unconditionally
in the Makefiles when building iproute2.

Signed-off-by: Sam James <sam@gentoo.org>
Signed-off-by: David Ahern <dsahern@kernel.org>

1 files changed, 1 insertions, 0 deletions

diff --git a/configure b/configure
index eb689341d..78bc52c00 100755
--- a/configure
+++ b/configure
@@ -445,6 +445,7 @@ EOF
 check_strlcpy()
 {
     cat >$TMPDIR/strtest.c <<EOF
+#define _GNU_SOURCE
 #include <string.h>
 int main(int argc, char **argv) {
 	char dst[10];