Define _POSIX_C_SOURCE

 src/c.zig | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/c.zig b/src/c.zig
index f7d66464..df4bceeb 100644
--- a/src/c.zig
+++ b/src/c.zig
@@ -16,7 +16,9 @@
 // along with this program. If not, see <https://www.gnu.org/licenses/>.
 
 pub usingnamespace @cImport({
+    @cDefine("_POSIX_C_SOURCE", "200809L");
     @cDefine("WLR_USE_UNSTABLE", {});
+
     @cInclude("time.h");
     @cInclude("stdlib.h");
     @cInclude("wayland-server-core.h");