librbspeex.a: simplify Makefile for OS X.
- As done with the libucl Makefile replace the universal library handling and
use ar to create a library from fat objects instead.
- Replace OUT with BUILD_DIR to be in line with the other Makefiles. As a
result librbspeex will now be build in a subfolder better named than "build"
when building with Rockbox Utility.
- Make the Makefile depend on the depencency file. This should fix problems
with a broken dependency file not being regenerated properly, causing the
build to fail.
git-svn-id: svn://svn.rockbox.org/rockbox/trunk@31587 a1c6a512-1295-4272-9138-f99709370657