Convert ODIN_OS and ODIN_ARCH to use enums rather than use strings

core/crypto/_fiat/field_poly1305/field.odin

@@ -22,7 +22,7 @@ fe_from_bytes :: #force_inline proc (out1: ^Tight_Field_Element, arg1: []byte, a
 
 	assert(len(arg1) == 16)
 
-	when ODIN_ARCH == "i386" || ODIN_ARCH == "amd64" {
+	when ODIN_ARCH == .i386 || ODIN_ARCH == .amd64 {
 		// While it may be unwise to do deserialization here on our
 		// own when fiat-crypto provides equivalent functionality,
 		// doing it this way provides a little under 3x performance

core/crypto/chacha20/chacha20.odin

@@ -346,7 +346,7 @@ _do_blocks :: proc (ctx: ^Context, dst, src: []byte, nr_blocks: int) {
 		// Until dedicated assembly can be written leverage the fact that
 		// the callers of this routine ensure that src/dst are valid.
 
-		when ODIN_ARCH == "i386" || ODIN_ARCH == "amd64" {
+		when ODIN_ARCH == .i386 || ODIN_ARCH == .amd64 {
 			// util.PUT_U32_LE/util.U32_LE are not required on little-endian
 			// systems that also happen to not be strict about aligned
 			// memory access.

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")
 	}