build: use new toolchain variables for tools

This change migrates the values of `CC`, `CPP`, `AS` and other toolchain
variables to the new `$(toolchain)-$(tool)` variables, which were
introduced by the toolchain refactor patch. These variables should be
equivalent to the values that they're replacing.

Change-Id: I644fe4ce82ef1894bed129ddb4b6ab94fb04985d
Signed-off-by: Chris Kay <chris.kay@arm.com>
diff --git a/tools/amlogic/Makefile b/tools/amlogic/Makefile
index d6d464b..5ff26e5 100644
--- a/tools/amlogic/Makefile
+++ b/tools/amlogic/Makefile
@@ -30,22 +30,20 @@
   Q :=
 endif
 
-HOSTCC := gcc
-
 .PHONY: all clean distclean
 
 all: ${PROJECT}
 
 ${PROJECT}: ${OBJECTS} Makefile
 	@echo "  HOSTLD  $@"
-	${Q}${HOSTCC} ${OBJECTS} -o $@
+	${Q}$(host-cc) ${OBJECTS} -o $@
 	@${ECHO_BLANK_LINE}
 	@echo "Built $@ successfully"
 	@${ECHO_BLANK_LINE}
 
 %.o: %.c Makefile
 	@echo "  HOSTCC  $<"
-	${Q}${HOSTCC} -c ${HOSTCCFLAGS} $< -o $@
+	${Q}$(host-cc) -c ${HOSTCCFLAGS} $< -o $@
 
 clean:
 	$(call SHELL_DELETE_ALL, ${PROJECT} ${OBJECTS})