tools: allow to override python

Not force to use python from PATH. Issue was noted when building with
Yocto, because python from the distro is always taken instead of
python-native built during Yocto process.

Signed-off-by: Stefano Babic <sbabic@denx.de>
CC: Simon Glass <sjg@chromium.org>
Reviewed-by: Simon Glass <sjg@chromium.org>

Makefile

@@ -348,7 +348,7 @@ OBJCOPY		= $(CROSS_COMPILE)objcopy
 OBJDUMP		= $(CROSS_COMPILE)objdump
 AWK		= awk
 PERL		= perl
-PYTHON		= python
+PYTHON		?= python
 DTC		= dtc
 CHECK		= sparse
 

tools/Makefile

@@ -120,7 +120,7 @@ _libfdt.so-sharedobjs += $(LIBFDT_OBJS)
 libfdt:
 
 tools/_libfdt.so: $(patsubst %.o,%.c,$(LIBFDT_OBJS)) tools/libfdt_wrap.c
-	LDFLAGS="$(HOSTLDFLAGS)" CFLAGS= python $(srctree)/lib/libfdt/setup.py \
+	LDFLAGS="$(HOSTLDFLAGS)" CFLAGS= ${PYTHON} $(srctree)/lib/libfdt/setup.py \
 		"$(_hostc_flags)" $^
 	mv _libfdt.so $@