Fails when file name is `cpp11.cpp`

[dfalbel]

cpp_source fails when the source file is called cpp11.cpp:
It will also fail if the file name contains . or -, but the error messages here are more informative.

writeLines('
[[cpp11::register]]
int add(int x, int y, int z) {
  int sum = x + y + z;
  return sum;
}', "cpp11.cpp")

cpp11::cpp_source("cpp11.cpp")
#> Error in (function (command = NULL, args = character(), error_on_status = TRUE, : System command 'R' failed, exit status: 1, stderr:
#> E> duplicate symbol '__cpp11_add' in:
#> E>     /private/var/folders/x0/fqbv9_ys1lq55xqjqbqllzqm0000gn/T/RtmpbkL1uf/file215a3ddf389a/src/cpp11.o
#> E> ld: 1 duplicate symbol for architecture x86_64
#> E> clang: error: linker command failed with exit code 1 (use -v to see invocation)
#> E> make: *** [/private/var/folders/x0/fqbv9_ys1lq55xqjqbqllzqm0000gn/T/RtmpbkL1uf/file215a3ddf389a/src/cpp11.so] Error 1

^{Created on 2020-11-27 by the reprex package (v0.3.0)}