[wasm] Add shims for aliased errno constants in WASILibc overlay

We provide shims for errno constants in WASILibc overlay since
wasi-libc's errno.h defines those constants in a way that cannot be
imported by ClangImporter.
However, some errno constants are aliased in wasi-libc, and we didn't
provided shims for them. This patch adds those missing shims.

Author: kateinoigakukun

stdlib/public/Platform/WASILibc.swift.gyb

@@ -73,6 +73,7 @@ posix_error_codes = [
   "EADDRNOTAVAIL",
   "EAFNOSUPPORT",
   "EAGAIN",
+  "EWOULDBLOCK",
   "EALREADY",
   "EBADF",
   "EBADMSG",
@@ -125,6 +126,7 @@ posix_error_codes = [
   "ENOTRECOVERABLE",
   "ENOTSOCK",
   "ENOTSUP",
+  "EOPNOTSUPP",
   "ENOTTY",
   "ENXIO",
   "EOVERFLOW",