ARCv2: Allow older gcc to cope with new regime of ARCv2/ARCompact support

-no-ll64 is specific to ARCv2 ISA, and is obviously not supported by
older ARC gcc - in this case the one hosted by linux-next sanity build
service.

Ensure that it doesn't get included for ISA_ARCOMPACT
Reported-by: Guenter Roeck <private@roeck-us.net>
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>

arch/arc/Makefile

@@ -37,7 +37,7 @@ cflags-$(CONFIG_ARC_HAS_LLSC)		+= -mlock
 cflags-$(CONFIG_ARC_HAS_SWAPE)		+= -mswape
 
 ifndef CONFIG_ARC_HAS_LL64
-cflags-y				+= -mno-ll64
+cflags-$(CONFIG_ISA_ARCV2)		+= -mno-ll64
 endif
 
 cflags-$(CONFIG_ARC_DW2_UNWIND)		+= -fasynchronous-unwind-tables