This fixes platform tag on Solaris/Illumos.

The problem is that os here can never be sunos, but rather solaris/illumos.

The following:

-                if os.starts_with("sunos") {
+                if os.starts_with("illumos") || os.starts_with("solaris") {

works as well, but checking the enum values seems nicer (and it's definitely faster). Using get_python_os would likely work as well, but I didn't go that way for the same reason.