os/os2: wasi target support

core/crypto/rand_generic.odin

@@ -5,6 +5,7 @@
 #+build !netbsd
 #+build !darwin
 #+build !js
+#+build !wasi
 package crypto
 
 HAS_RAND_BYTES :: false

core/crypto/rand_wasi.odin

@@ -0,0 +1,13 @@
+package crypto
+
+import "core:fmt"
+import "core:sys/wasm/wasi"
+
+HAS_RAND_BYTES :: true
+
+@(private)
+_rand_bytes :: proc(dst: []byte) {
+	if err := wasi.random_get(dst); err != nil {
+		fmt.panicf("crypto: wasi.random_get failed: %v", err)
+	}
+}