package/refpolicy: set python path

Set python path to $(HOST_DIR)/usr/bin/python to avoid build failures if
python3 found on host is broken

Fixes:
 - http://autobuild.buildroot.org/results/1f878405593dd05bb00fe0b06ca1c64ffbe6c572

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

package/refpolicy/refpolicy.mk

@@ -26,6 +26,7 @@ endif
 
 # Cannot use multiple threads to build the reference policy
 REFPOLICY_MAKE = \
+	PYTHON=$(HOST_DIR)/usr/bin/python \
 	TEST_TOOLCHAIN=$(HOST_DIR) \
 	$(TARGET_MAKE_ENV) \
 	$(MAKE1)