armstubs: Define the new symbols use in Makefile

The tools repository renamed the CC, LD etc symbols to CC7, LD7 etc.
See:
https://github.com/raspberrypi/tools/commit/b0c869bc929587a7e1d20a98e2dc828a24ca396a

Signed-off-by: Andrei Gherzan <andrei@gherzan.ro>

recipes-bsp/armstubs/armstubs.bb

@@ -11,6 +11,10 @@ COMPATIBLE_MACHINE = "^rpi$"
 
 S = "${RPITOOLS_S}/armstubs"
 
+export CC7="${CC}"
+export LD7="${LD}"
+export OBJCOPY7="${OBJCOPY}"
+export OBJDUMP7="${OBJDUMP}"
 export CC8="${CC}"
 export LD8="${LD}"
 export OBJCOPY8="${OBJCOPY}"