libnss: fix 64-bit build

On some architectures (found on x86_64, but probably others too),
libnss builds with -m32 unless it is configured for 64-bit build.  So
force 64-bit build on 64-bit architectures.

Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/libnss/libnss.mk

@@ -28,6 +28,10 @@ LIBNSS_BUILD_VARS = MOZILLA_CLIENT=1 \
 		OS_RELEASE="2.6" \
 		OS_TEST="$(ARCH)"
 
+ifeq ($(BR2_ARCH_IS_64),y)
+LIBNSS_BUILD_VARS += USE_64=1
+endif
+
 
 define LIBNSS_BUILD_CMDS
 	$(MAKE1) -C $(@D)/$(LIBNSS_SUBDIR)/nss build_coreconf build_dbm all \