xz: use update-alternatives

Installing xz and busybox together may cause conflicts for xz, xzcat,
unxz, and their lzma variants. In the default configuration, xzcat is
silently replaced with a symlink to busybox. If busybox is compiled with
CONFIG_XZ=y, its postinst fails during do_rootfs.

Using update-alternatives to xz handles these conflicts properly.

(From OE-Core rev: e48cd8423562d4b03bdf55ba04873b7582f12452)

Signed-off-by: Allen Wild <allenwild93@gmail.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-extended/xz/xz_5.2.3.bb

@@ -31,6 +31,11 @@ PACKAGES =+ "liblzma"
 
 FILES_liblzma = "${libdir}/liblzma*${SOLIBS}"
 
+inherit update-alternatives
+ALTERNATIVE_PRIORITY = "100"
+ALTERNATIVE_${PN} = "xz xzcat unxz \
+                     lzma lzcat unlzma"
+
 BBCLASSEXTEND = "native nativesdk"
 
 export CONFIG_SHELL="/bin/sh"