busybox: Use base_bindir instead of hardcoding /bin path

busybox: Use base_bindir instead of hardcoding /bin path

This symlink is not valid when using usrmerge and ptest packaging would fail

Exception: FileExistsError: [Errno 17] File exists: '/usr/bin/busybox.suid' -> '/mnt/b/yoe/master/build/tmp/work/ppc64p9le-yoe-linux-musl/busybox/1.35.0-r0/package/usr/lib/busybox/ptest/bin/login'

Signed-off-by: Khem Raj <raj.khem@gmail.com>
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
(cherry picked from commit 238fd30689054c7b44176dce7180fb6dac4e1b6f)
Signed-off-by: Steve Sakoman <steve@sakoman.com>