make.py (and the pymake modules that support it) are an implementation of the make tool which are mostly compatible with makefiles written for GNU make. http://benjamin.smedbergs.us/pymake/
You need to have a Windows build environment installed.
Anywhere you would normally type 'make', instead type 'python -OO /path/to/srcdir/build/pymake/make.py'. For example:
- Instead of 'make -f client.mk' to start a build, you would type 'python -OO build/pymake/make.py -f client.mk'.
- To run tests instead of typing 'make mochitest-plain' in the object directory, you would type 'python -OO ../build/pymake/make.py mochitest-plain'.
Unlike gmake on Windows, pymake is capable of doing parallel builds, so you can set a MOZ_MAKE_FLAGS=-jN in your mozconfig without risk of deadlocks.