intel/perf: adapt to platforms like Solaris without d_type in struct dirent

intel/perf: adapt to platforms like Solaris without d_type in struct dirent

Signed-off-by: Alan Coopersmith <alan.coopersmith@oracle.com>
[Eric: factor out the is_dir_or_link() check and fix a bug in v1]
Signed-off-by: Eric Engestrom <eric.engestrom@intel.com>
v3: include directory path when lstat'ing files
v4: fix inverted check in enumerate_sysfs_metrics()

Reviewed-by: Eric Engestrom <eric.engestrom@intel.com>
Tested-by: Marge Bot <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/2258>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/2258>