Makefile.system: remove duplicate variable GCCVERSIONGT5
... to bring unified gcc version detection with common variables to the
one remaining spot in Makefile.system.
@@ -606,7 +606,6 @@ ifneq ($(C_COMPILER), GCC)
DYNAMIC_CORE += POWER9
endif
ifeq ($(C_COMPILER), GCC)
-GCCVERSIONGT5 := $(shell expr `$(CC) -dumpversion | cut -f1 -d.` \> 5)
ifeq ($(GCCVERSIONGT5), 1)
DYNAMIC_CORE += POWER9
else
