add get thread count to openbsd

core/os/os_openbsd.odin

@@ -269,6 +269,7 @@ foreign libc {
 	@(link_name="mkdir")	_unix_mkdir	:: proc(path: cstring, mode: mode_t) -> c.int ---
 
 	@(link_name="getpagesize") _unix_getpagesize :: proc() -> c.int ---
+	@(link_name="sysconf") _sysconf :: proc(name: c.int) -> c.long ---
 	@(link_name="fdopendir") _unix_fdopendir :: proc(fd: Handle) -> Dir ---
 	@(link_name="closedir")	_unix_closedir	:: proc(dirp: Dir) -> c.int ---
 	@(link_name="rewinddir") _unix_rewinddir :: proc(dirp: Dir) ---
@@ -704,6 +705,11 @@ get_page_size :: proc() -> int {
 	return page_size
 }
 
+_SC_NPROCESSORS_ONLN :: 503
+get_processor_thread_count :: proc() -> int {
+	thread_count := int(_sysconf(_SC_NPROCESSORS_ONLN))
+	return thread_count
+}
 
 _alloc_command_line_arguments :: proc() -> []string {
 	res := make([]string, len(runtime.args__))
@@ -711,4 +717,4 @@ _alloc_command_line_arguments :: proc() -> []string {
 		res[i] = string(arg)
 	}
 	return res
-}
+}