Makefiles: do not force using GCC <= 6
The code has been updated to work with GCC up to 9.2.1
so there's no longer a need to use GCC 6.x or lower. Yay!
#------------------ start of linux-elf/COMMON/defines ---------------------
#
# $Header: /cvs/stx/stx/configurations/linux-elf/COMMON/defines,v 1.92 2016-07-19 19:56:46 stefan Exp $
include $(MAKELIB)/config.make
CCARCHCOMMONOPT=-DELF
#RELOCINSTVARS=+relocInstvars
INTERN_H=linuxIntern.h
CPUINTERN_H=$(INCLUDE)/linuxIntern.h
OS=-DLINUX
MAKEFILE_EXTENSION=linux-elf
SETUP_RULE=setup_linux