added support for cmd.exe as a shell on make.

tools/top.mk

@@ -2,6 +2,12 @@ ifneq ($(lastword a b),b)
 $(error This Makefile require make 3.81 or newer)
 endif
 
+# Detect windows or not
+# https://stackoverflow.com/questions/714100/os-detecting-makefile/52062069#52062069
+ifeq '$(findstring ;,$(PATH))' ';'
+UNAME := Windows
+endif
+
 # Set TOP to be the path to get from the current directory (where make was
 # invoked) to the top of the tree. $(lastword $(MAKEFILE_LIST)) returns
 # the name of this makefile relative to where make was invoked.
@@ -9,9 +15,16 @@ endif
 THIS_MAKEFILE := $(lastword $(MAKEFILE_LIST))
 TOP := $(patsubst %/tools/top.mk,%,$(THIS_MAKEFILE))
 
+ifeq ($(UNAME),Windows)
+TOP := $(subst \,/,$(shell for %%i in ( $(TOP) ) do echo %%~fi))
+else
 TOP := $(shell realpath $(TOP))
-
+endif
 #$(info Top directory is $(TOP))
 
+ifeq ($(UNAME),Windows)
+CURRENT_PATH := $(subst $(TOP)/,,$(subst \,/,$(shell echo %CD%)))
+else
 CURRENT_PATH := $(shell realpath --relative-to=$(TOP) `pwd`)
+endif
 #$(info Path from top is $(CURRENT_PATH))