Now they recognize arm-linux-androideabi toolchain

Upstream should set Libs.private, but we want Libs.

This reverts commit 878d5212.
This fixes the build with installed autopoint.

we don't use 'xz' binary directly

use $(AUTOCONF) to make pkg-config, add dependancy on autoconf

Signed-off-by: Rafaël Carré <funman@videolan.org>

This makes sure our build of tar (if it exists) is used before system tar

We need -arch to specify which arch to be built, else we have no idea