The function strerror_r returns an int per POSIX spec, but GNU version
returns char *. Using it fails the compilation in Alpine, so use
_nm_strerror_r instead that handles both cases.
Fixes: 41e28b900f ('daemon-helper: add read-file-as-user')
Add a new command to read the content of a file after switching to the
given user. This command can be used to enforce Unix filesystem
permissions when accessing a file on behalf of a user.
We have nm_strerror_native_r(), which is the wrapper around strerror_r() that
we want to use in glib components (it also will ensure that the string is valid
UTF-8). However, it's not usable from non-glib components.
Move the part that abstracts strerror_r() out to libnm-std-aux as _nm_strerror_r().
The purpose is that non-glib componenent can use the thread-safe wrapper around
strerror_r().
