cmake: fix use of unsupported -fno-pie with xcc

The commit 8259931f ("xcc-clang: Do not used unavailable options")
has a side-effect that builds with xcc default to use -fno-pie. This
is not a supported compiler option for xcc, resulting in failing builds.

Use same configuration for xcc as is in place for xcc-clang, and
do not use -fno-pie.

Signed-off-by: Kai Vehmanen <kai.vehmanen@linux.intel.com>