[PATCH] Makefile: sanitize rpath and quieten the strip command

- Use ccdv to run strip (yes, a really cosmetic change)

- Use the proper rpath when linking libcpufreq.so. It is needed
  because otherwise libtool will create a messed libdir in
  libcpufreq.la fooling 3rd parties linking against libcpufreq (and
  using libtool for themselves).
  Since the problem is the usage of $(DESTDIR) this will probably only
  show in prebuilt packages in linux distros.

Signed-off-by: Mattia Dongili <malattia@linux.it>
Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>