project_config_mk: fix if condition
COMPONENT_KCONFIGS := $(foreach component,$(COMPONENT_PATHS),$(wildcard $(component)/Kconfig))
COMPONENT_KCONFIGS_PROJBUILD := $(foreach component,$(COMPONENT_PATHS),$(wildcard $(component)/Kconfig.projbuild))
-ifdef MSYSTEM
+ifeq ($(OS),Windows_NT)
# kconfiglib requires Windows-style paths for kconfig files
COMPONENT_KCONFIGS := $(shell cygpath -w $(COMPONENT_KCONFIGS))
COMPONENT_KCONFIGS_PROJBUILD := $(shell cygpath -w $(COMPONENT_KCONFIGS_PROJBUILD))
