wasm: allow all undefined symbols

Undefined symbols will be shown by the embedder, for example when
running generated wasm files in a browser.

In the future, this should probably become a fixed list again. But for
experimenting it's easier now to just ignore undefined symbols and
expect the JS to provide them.

targets/wasm.json

@@ -4,7 +4,7 @@
 	"linker":        "ld.lld-7",
 	"pre-link-args": [
 		"-flavor", "wasm",
-		"-allow-undefined-file", "targets/wasm.syms"
+		"-allow-undefined"
 	],
 	"emulator":      ["cwa"]
 }

targets/wasm.syms

@@ -1,2 +0,0 @@
-io_get_stdout
-resource_write