Change the default compiler of the extensions from the fixed gcc
to $(CC) passed in by the upper layer Makefile,
to facilitate cross_compile.

Signed-off-by: jianyun.gao <jianyungao89@gmail.com>
---
 Makefile            |  2 +-
 extensions/Makefile | 10 +++++-----
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/Makefile b/Makefile
index b277129..58b1326 100644
--- a/Makefile
+++ b/Makefile
@@ -727,7 +727,7 @@ extensions: make_configure
    @$(MAKE) do_extensions
 
 do_extensions:
-   @$(MAKE) -C extensions -i TARGET=$(TARGET) TARGET_CFLAGS="$(CFLAGS) $(TARGET_CFLAGS)" GDB=$(GDB) GDB_FLAGS=$(GDB_FLAGS)
+   @$(MAKE) -C extensions -i CC=$(CC) TARGET=$(TARGET) TARGET_CFLAGS="$(CFLAGS) $(TARGET_CFLAGS)" GDB=$(GDB) GDB_FLAGS=$(GDB_FLAGS)
 
 memory_driver: make_configure
    @$(MAKE) -C memory_driver -i
diff --git a/extensions/Makefile b/extensions/Makefile
index e4c68c3..67d3839 100644
--- a/extensions/Makefile
+++ b/extensions/Makefile
@@ -23,7 +23,7 @@
 # suffice, create a .mk file with the same prefix as the .c file,
 # and that makefile will be invoked.
 #
-
+CC ?= gcc
 CONTRIB_SO := $(patsubst %.c,%.so,$(wildcard *.c))
 
 all: link_defs $(CONTRIB_SO)
@@ -37,11 +37,11 @@ $(CONTRIB_SO): %.so: %.c defs.h
        $(MAKE) -f $*.mk; \
    else \
        grep -q '((constructor))' $*.c && { \
-           echo "gcc -Wall -g -shared -rdynamic -o $@ $*.c -fPIC -D$(TARGET) $(TARGET_CFLAGS) $(GDB_FLAGS)"; \
-           gcc -Wall -g -shared -rdynamic -o $@ $*.c -fPIC -D$(TARGET) $(TARGET_CFLAGS) $(GDB_FLAGS); \
+           echo "$(CC) -Wall -g -shared -rdynamic -o $@ $*.c -fPIC -D$(TARGET) $(TARGET_CFLAGS) $(GDB_FLAGS)"; \
+           $(CC) -Wall -g -shared -rdynamic -o $@ $*.c -fPIC -D$(TARGET) $(TARGET_CFLAGS) $(GDB_FLAGS); \
        } || { \
-           echo "gcc -Wall -g -nostartfiles -shared -rdynamic -o $@ $*.c -fPIC -D$(TARGET) $(TARGET_CFLAGS) $(GDB_FLAGS)"; \
-           gcc -Wall -g -nostartfiles -shared -rdynamic -o $@ $*.c -fPIC -D$(TARGET) $(TARGET_CFLAGS) $(GDB_FLAGS); \
+           echo "$(CC) -Wall -g -nostartfiles -shared -rdynamic -o $@ $*.c -fPIC -D$(TARGET) $(TARGET_CFLAGS) $(GDB_FLAGS)"; \
+           $(CC) -Wall -g -nostartfiles -shared -rdynamic -o $@ $*.c -fPIC -D$(TARGET) $(TARGET_CFLAGS) $(GDB_FLAGS); \
        }; \
    fi
 
--
2.34.1