nu801: Mark as nonshared to build in step 1

Mark the package as nonshared to build it in the target specific build
step 1 of the build bots instead of the architecture generic build step 2.

In the build step 2 it may be left out if we build it using a different
target.

Fixes: #16857
Link: https://github.com/openwrt/openwrt/pull/16859
Signed-off-by: Robert Marko <robimarko@gmail.com>

package/system/gpio-cdev/nu801/Makefile

@@ -3,6 +3,7 @@
 include $(TOPDIR)/rules.mk
 
 PKG_NAME:=nu801
+PKG_FLAGS:=nonshared
 PKG_RELEASE:=1
 
 PKG_SOURCE_PROTO:=git