win-build: Explicity call phyton

In some windows systems, executing a python script requires to call
the python interpreter explicitly.

Jira: ZEP-517

Change-Id: Ic039bb22618b0bfa224a2ca0c4198e1bc4d391d7
Signed-off-by: Juan Manuel Cruz <[email protected]>

Author: jmnlcruz

Kbuild

@@ -50,7 +50,9 @@ misc/generated/sysgen/prj.mdef:	$(MDEF_FILE_PATH) \
 misc/generated/sysgen/kernel_main.c: misc/generated/sysgen/prj.mdef \
 				     kernel/microkernel/include/micro_private_types.h \
 				     kernel/microkernel/include/kernel_main.h
-	$(Q)$(srctree)/scripts/sysgen $(CURDIR)/misc/generated/sysgen/prj.mdef $(CURDIR)/misc/generated/sysgen/
+	$(Q)$(PYTHON) $(srctree)/scripts/sysgen \
+			$(CURDIR)/misc/generated/sysgen/prj.mdef \
+			$(CURDIR)/misc/generated/sysgen/
 
 define filechk_configs.c
 	(echo "/* file is auto-generated, do not modify ! */"; \