message: add isystem include variant
diff: @@ -162,7 +162,7 @@ GCCINCLUDEPATHSB := $(shell cygpath -u $(GCCINCLUDEPATHSA))
  GCCINCLUDEPATHS := $(GCCINCLUDEPATHSB:%=-I%)
  endif
  else
  -GCCINCLUDEPATHS := $(INCLUDEPATHS:%=-I%) $(COMMONINCLUDEPATHS:%=-I%)
  +GCCINCLUDEPATHS := $(INCLUDEPATHS:%=-I%) $(COMMONINCLUDEPATHS:%=-I%) $(INCLUDEPATHSSYSTEM:%=-isystem %)
  endif
  VSINCLUDEPATHS := $(INCLUDEPATHS:%=/I%) $(COMMONINCLUDEPATHS:%=/I%)
  