[SPARC64]: Use $(CC) in NEW_GCC checks.

arch/sparc64/Makefile

@@ -10,7 +10,7 @@
 
 AFLAGS_vmlinux.lds.o += -Usparc
 
-CC		:= $(shell if gcc -m64 -S -o /dev/null -xc /dev/null >/dev/null 2>&1; then echo gcc; else echo sparc64-linux-gcc; fi )
+CC		:= $(shell if $(CC) -m64 -S -o /dev/null -xc /dev/null >/dev/null 2>&1; then echo $(CC); else echo sparc64-linux-gcc; fi )
 
 NEW_GCC := $(shell if $(CC) -m64 -mcmodel=medlow -S -o /dev/null -xc /dev/null >/dev/null 2>&1; then echo y; else echo n; fi; )
 NEW_GAS := $(shell if $(LD) -V 2>&1 | grep 'elf64_sparc' > /dev/null; then echo y; else echo n; fi)