package/libwpe: drop rpi-userland specific tweak

As we're about to remove the rpi-userland package, drop the special
tweak for it from package/libwpe.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Reviewed-by: Adrian Perez de Castro <aperez@igalia.com>
Signed-off-by: Julien Olivain <ju.o@free.fr>

package/libwpe/libwpe.mk

@@ -16,10 +16,4 @@ LIBWPE_DEPENDENCIES = libegl libxkbcommon
 LIBWPE_CFLAGS = $(TARGET_CFLAGS)
 LIBWPE_CXXFLAGS = $(TARGET_CXXFLAGS)
 
-# Workaround for https://github.com/raspberrypi/userland/issues/316
-ifeq ($(BR2_PACKAGE_RPI_USERLAND),y)
-LIBWPE_CFLAGS += -D_GNU_SOURCE
-LIBWPE_CXXFLAGS += -D_GNU_SOURCE
-endif
-
 $(eval $(meson-package))