Issue: usethis::use_rcpp_armadillo() Generates CXX_STD=CXX1, Leading to CRAN Note on C++11 Specification

Description:

When using the usethis::use_rcpp_armadillo() function, it generates src/Makevars and src/Makevars.win with CXX_STD=CXX1 . Running devtools::check() subsequently raises a note:

checking C++ specification ... NOTE 

Specified C++11: please drop specification unless essential

This issue creates a non-compliance with CRAN standards, requiring that the line, containing CXX_STD=CXX1, is manually removed in both files.

Steps to Reproduce:

1. Call the usethis::use_rcpp_armadillo(name = "cppcode") function.
2. Run devtools::check().
3. Observe the note regarding the C++11 specification.

Expected Behavior:

The function should generate src/Makevars and src/Makevars.win without CXX_STD=CXX1 or handle this in a way that aligns with CRAN's requirements.

Actual Behavior:

The line CXX_STD=CXX1 is generated, leading to a note during the check process, and manual removal is required to conform to CRAN.

Suggested Fix:

Either omit this line or handle it in a way that is compatible with CRAN standards.

System Information:

• usethis version: 2.2.2
• devtools version 2.4.5
• R version: 4.3.1
• Operating System: Ubuntu 22.04.2 LTS