cfg-lexer: fix handling of glob return values on musl

[bazsi]

In case an error happens during glob(), glibc returns GLOB_NOMATCH while musl returns GLOB_ABORTED. Handle both properly.

[bazsi]

One additional context: glibc seems to ignore ENOTDIR errors, while musl does not. So to trigger the issue, one needs to

@include "foo/*/*.conf"

and then place a symlink to "foo/" that points to an existing file. In this case, glob finds the symlink, tries to use it as a directory, fails with ENOTDIR. On musl, this calls the glob error callback and prints:

Error processing path for inclusion; path='/etc/syslog-ng/foo/symlink/', errno='Not a directory (20)'

and then returns GLOB_ABORTED.

Our wrapper function was incorrectly returning success in this case, without the include file list being populated and then it crashes.