[R] CRAN `NOTE` about Makevars

[jonkeane]

Describe the enhancement requested

This might be transient, since I only see it in this one job, but it also is possible that it is only configured to be checked on this one job. https://www.r-project.org/nosvn/R.check/r-devel-linux-x86_64-fedora-clang/arrow-00check.html

checking compilation flags in Makevars ... NOTE
Package has both ‘src/Makevars.in’ and ‘src/Makevars’.
Installation with --no-configure' is unlikely to work.  If you intended
‘src/Makevars’ to be used on Windows, rename it to ‘src/Makevars.win’
otherwise remove it.  If ‘configure’ created ‘src/Makevars’, you need a
‘cleanup’ script.

It should be easy enough to resolve if we have to though.

Component(s)

R