It fails because you installed R in C:\Program Files\R even though the FAQ for R on Windows tells you not to install R in a path with spaces. See "Question 2.2: How do I install R for Windows":
If you want to be able to build packages from sources, we recommend
that you choose an installation path not containing spaces.
The Rcpp / RInside documentaion repeats that recommendation. Do not install R in a path with spaces. If you must, you have to fix the Makefile to avoid the path expansion from breaking.
