Convert ODIN_OS and ODIN_ARCH to use enums rather than use strings

core/crypto/rand_generic.odin

@@ -1,6 +1,6 @@
 package crypto
 
-when ODIN_OS != "linux" {
+when ODIN_OS != .Linux {
 	_rand_bytes :: proc (dst: []byte) {
 		unimplemented("crypto: rand_bytes not supported on this OS")
 	}