build: Introduce HOSTCC flag

Tools are built using the compiler specified in `HOSTCC` instead of
reusing the `CC` variable.  By default, gcc is used.

Change-Id: I83636a375c61f4804b4e80784db9d061fe20af87
Signed-off-by: dp-arm <dimitris.papastamos@arm.com>

Makefile

@@ -113,6 +113,9 @@ endif
 # Toolchain
 ################################################################################
 
+HOSTCC			:=	gcc
+export HOSTCC
+
 CC			:=	${CROSS_COMPILE}gcc
 CPP			:=	${CROSS_COMPILE}cpp
 AS			:=	${CROSS_COMPILE}gcc

tools/cert_create/Makefile

@@ -64,7 +64,7 @@ INC_DIR := -I ./include -I ${PLAT_INCLUDE} -I ${OPENSSL_DIR}/include
 LIB_DIR := -L ${OPENSSL_DIR}/lib
 LIB := -lssl -lcrypto
 
-CC := gcc
+HOSTCC ?= gcc
 
 .PHONY: all clean realclean
 
@@ -75,11 +75,11 @@ ${BINARY}: ${OBJECTS} Makefile
 	@echo 'const char build_msg[] = "Built : "__TIME__", "__DATE__; \
                 const char platform_msg[] = "${PLAT_MSG}";' | \
                 ${CC} -c ${CFLAGS} -xc - -o src/build_msg.o
-	${Q}${CC} src/build_msg.o ${OBJECTS} ${LIB_DIR} ${LIB} -o $@
+	${Q}${HOSTCC} src/build_msg.o ${OBJECTS} ${LIB_DIR} ${LIB} -o $@
 
 %.o: %.c
 	@echo "  CC      $<"
-	${Q}${CC} -c ${CFLAGS} ${INC_DIR} $< -o $@
+	${Q}${HOSTCC} -c ${CFLAGS} ${INC_DIR} $< -o $@
 
 clean:
 	$(call SHELL_DELETE_ALL, src/build_msg.o ${OBJECTS})

tools/fiptool/Makefile

@@ -29,7 +29,7 @@ endif
 
 INCLUDE_PATHS := -I. -I../../include/tools_share
 
-CC := gcc
+HOSTCC ?= gcc
 
 .PHONY: all clean distclean
 
@@ -37,7 +37,7 @@ all: ${PROJECT} fip_create
 
 ${PROJECT}: ${OBJECTS} Makefile
 	@echo "  LD      $@"
-	${Q}${CC} ${OBJECTS} -o $@ ${LDLIBS}
+	${Q}${HOSTCC} ${OBJECTS} -o $@ ${LDLIBS}
 	@${ECHO_BLANK_LINE}
 	@echo "Built $@ successfully"
 	@${ECHO_BLANK_LINE}
@@ -48,7 +48,7 @@ fip_create: fip_create.sh
 
 %.o: %.c %.h Makefile
 	@echo "  CC      $<"
-	${Q}${CC} -c ${CPPFLAGS} ${CFLAGS} ${INCLUDE_PATHS} $< -o $@
+	${Q}${HOSTCC} -c ${CPPFLAGS} ${CFLAGS} ${INCLUDE_PATHS} $< -o $@
 
 clean:
 	$(call SHELL_DELETE_ALL, ${PROJECT} ${OBJECTS} fip_create)