xcc-clang: Do not used unavailable options

xcc-clang in based on clan-10 and does not support -fno-pic and
-fno-pie.

clang-10: warning: argument unused during compilation: '-fno-pic'
[-Wunused-command-line-argument]
[147/148] Linking C executable zephyr/zephyr.elf
clang-10: warning: argument unused during compilation: '-no-pie'
[-Wunused-command-line-argument]

Signed-off-by: Flavio Ceolin <flavio.ceolin@intel.com>