base-files: add ARCH_PACKAGES to openwrt_release and os-release

Knowing the package architecture at runtime can be useful, e.g. to
configure opkg repository URLs. The value of ARCH_PACKAGES ("%A" in
VERSION_SED) as added to openwrt_release (as DISTRIB_ARCH) and os-release
(as LEDE_ARCH).

Signed-off-by: Matthias Schiffer <mschiffer@universe-factory.net>

package/base-files/files/usr/lib/os-release

@@ -9,6 +9,7 @@ BUG_URL="%b"
 SUPPORT_URL="%s"
 BUILD_ID="%R"
 LEDE_BOARD="%S"
+LEDE_ARCH="%A"
 LEDE_TAINTS="%t"
 LEDE_DEVICE_MANUFACTURER="%M"
 LEDE_DEVICE_MANUFACTURER_URL="%m"