[ros-svn] [chorns] 14520: Accept ROS_INSTALL environment variable

[chorns at svn.reactos.com]

Accept ROS_INSTALL environment variable


Updated files:
branches/xmlbuildsystem/reactos/Makefile
branches/xmlbuildsystem/reactos/tools/rbuild/backend/mingw/mingw.cpp
branches/xmlbuildsystem/reactos/tools/rbuild/backend/mingw/mingw.h
branches/xmlbuildsystem/reactos/tools/rbuild/backend/mingw/modulehandler.cpp
branches/xmlbuildsystem/reactos/tools/rbuild/tests/functiontest.cpp