Use of install.libs.R in an R package

use_install_libs.R

## Create a minimal buildable package
library(devtools)
create('testpkg')

## Write src/install.libs.R
dir.create('testpkg/src')
test.file <- path.expand('~/testfile.txt')
diag.lines <- c(
  deparse(quote(stop('This should break the installation'))),
  deparse(quote(file.create(test.file)))
)
writeLines(diag.lines,
           'testpkg/src/install.libs.R')

## Install package
## also tried manually with R CMD INSTALL
install('testpkg')

## The installation did not break
## nor the file has been created
file.exists('~/testfile.txt')   # FALSE

## Cleanup
remove.packages('testpkg')
unlink('testpkg', recursive = TRUE)

Thanks to Duncan Murdoch from R-package-devel mailing list for the answer:

The problem with the sample is that it has no
files in src that trigger processing: those would be Makefile,
Makefile.win, Makevars, or source files in supported languages.

If the real example doesn't have any of these (e.g. because it is just
copying a pre-compiled file from somewhere; not something you should do
in a CRAN package, but maybe reasonable in a local one), then the
easiest workaround is just to add an empty Makevars file.