I\'ve managed to get the Rcpp.package.skeleton to INSTALL in Windows by the following commands at the R prompt -
Rcpp.package.skeleton(\"mypackage\"
The package is tested extensively before every release, including on the Windows-using Win-builder. The regression tests even include building a package this way via a call to package.skeleton().
It is also rebuilt by CRAN post-release. Many people use it.
For all of those people, tests are appropriate and when long long cannot be used, it is #define-d away.
Now, you insist on building in a non-standard way: no source I know of recommends calling R CMD INSTALL via system(). I suspect you simply have a $PATH mishap and find another wrong g++ version.
I would suggest to do what the documentation suggests and run
R CMD INSTALL mypackage*tar.gz
in a cmd.exe prompt.