binutils-cross: Build with --enable-shared and install libiberty-pic.a

binutils-cross: Build with --enable-shared and install libiberty-pic.a

* On systems where PIC matters (e.g. MIPS, x86_64) building target
  binutils fails because its configured with --enable-shared but
  when it tried to link a shared library (libopcode.so) then it
  pulls in libiberty.a from the sysroot which is installed by
  binutils-cross earlier. This version however is a static archive
  and linking it with shared libraries not only does not work but
  is wrong too.

* This patch builds binutils-cross with --enable-shared and installs
  the PIC version of libiberty.a into sysroot as libiberty_pic.a
  now when target binutils is configured with --enable-shared and
  searches for PIC version of libiberty.a then it finds it
  correctly.

* Move INC_PR to binutils.inc. Also noticed that several recipes
  do not use binutils.inc so did not touch them

Signed-off-by: Khem Raj <raj.khem@gmail.com>