Windows Build Fixes GNU make 4.2.1 (#502)

After update of GNU make the tests for Windows OS are no longer needed. Note that GNU make 4.2.1 is used to build BMP under Windows OS.
Make native working

Again, the newer version of GCC make does not need the OS tests.

src/Makefile

@@ -99,12 +99,8 @@ $(TARGET): include/version.h $(OBJ)
 
 clean:	host_clean
 	$(Q)echo "  CLEAN"
-ifeq ($(OS), Windows_NT)
-	-$(Q)$(shell del *.o, *.d, blackmagic*, $(HOSTFILES))
-else
 	-$(Q)$(RM) *.o *.d *~ blackmagic $(HOSTFILES)
 	-$(Q)$(RM) platforms/*/*.o platforms/*/*.d mapfile include/version.h
-endif
 
 all_platforms:
 	$(Q)set -e ;\
@@ -130,9 +126,5 @@ command.c: include/version.h
 
 include/version.h: FORCE
 	$(Q)echo " GIT include/version.h"
-ifeq ($(OS), Windows_NT)
-	$(Q)echo #define FIRMWARE_VERSION "$(shell git describe --always --dirty)" > $@
-else
 	$(Q)echo "#define FIRMWARE_VERSION \"$(shell git describe --always --dirty)\"" > $@
-endif
 -include *.d

src/platforms/native/Makefile.inc

@@ -34,8 +34,4 @@ blackmagic_dfu: usbdfu.o dfucore.o dfu_f1.o
 	$(Q)$(CC) $^ -o $@ $(LDFLAGS_BOOT)
 
 host_clean:
-ifeq ($(OS), Windows_NT)
-	-$(Q)$(shell del blackmagic.bin blackmagic_dfu blackmagic_dfu.bin blackmagic_dfu.hex)
-else
 	-$(Q)$(RM) blackmagic.bin blackmagic_dfu blackmagic_dfu.bin blackmagic_dfu.hex
-endif