cc/gcc: simplify calls to core backend

The core backend is going to have more parameters in the upcoming
patches, so it will be a bit complex to handle.

Introduce an array-variable that is filled by the different code-paths
with the required values.

This makes the code easier to read and maintain.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@anciens.enib.fr>

 python

 import sys

 sys.path.insert(0, '@@PREFIX@@/share/gcc-@@VERSION@@/python')

 from libstdcxx.v6.printers import register_libstdcxx_printers

 register_libstdcxx_printers (None)

 end