https://bugs.gentoo.org/971850
_GNU_SOURCE was lost in some places with: https://github.com/libuv/libuv/commit/5c19f73aa206fcd2be55e2f20aaa8939b3cc5ff9
--- a/Makefile.am
+++ b/Makefile.am
@@ -479,6 +479,7 @@ endif
 
 if HURD
 uvinclude_HEADERS += include/uv/posix.h
+libuv_la_CFLAGS += -D_GNU_SOURCE
 libuv_la_SOURCES += src/unix/bsd-ifaddrs.c \
                     src/unix/no-fsevents.c \
                     src/unix/no-proctitle.c \