Fix use of errno on OpenBSD.

base/runtime/os_specific_bsd.odin

@@ -9,7 +9,7 @@ foreign libc {
 	@(link_name="write")
 	_unix_write :: proc(fd: i32, buf: rawptr, size: int) -> int ---
 
-	when ODIN_OS == .NetBSD {
+	when ODIN_OS == .NetBSD || ODIN_OS == .OpenBSD {
 		@(link_name="__errno") __error :: proc() -> ^i32 ---
 	} else {
 		__error :: proc() -> ^i32 ---

core/os/os_openbsd.odin

@@ -343,7 +343,7 @@ AT_REMOVEDIR        :: 0x08
 
 @(default_calling_convention="c")
 foreign libc {
-	@(link_name="__error")        __error              :: proc() -> ^c.int ---
+	@(link_name="__errno")        __error              :: proc() -> ^c.int ---
 
 	@(link_name="fork")           _unix_fork           :: proc() -> pid_t ---
 	@(link_name="getthrid")       _unix_getthrid       :: proc() -> int ---