build_helpers: Fix build config for CS310 with PACBTI in pp_test

Replace corstone300 with corstone310 for CS310 build with GCC
and PAC-BTI option.
Also amend the generated config as it appears in CI: GCC instead
of GNUARM

Signed-off-by: Nicola Mazzucato <nicola.mazzucato@arm.com>
Change-Id: I411c345e12466c690e75e0cbbc61ded90f222300
1 file changed