Export PATH and ERRNO_CODES from Emscripten. ### Description

Fixes #2577 by exporting `PATH` and `ERRNO_CODES` from Emscripten

### Checklists

- [x] Add a [CHANGELOG](https://github.com/pyodide/pyodide/blob/main/docs/project/changelog.md) entry
- [x] Add / update tests
- [x] Add new / update outdated documentation

From 88529d19154fae757a58229e76c0fb849d279725 Mon Sep 17 00:00:00 2001
From: Roman Yurchak <rth.yurchak@gmail.com>
Date: Mon, 28 Feb 2022 00:53:53 -0500
Subject: [PATCH 03/10] fix Py_Sigset_Converter

---
 Modules/posixmodule.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/Modules/posixmodule.c b/Modules/posixmodule.c
index 03de470323..b115552dcd 100644
--- a/Modules/posixmodule.c
+++ b/Modules/posixmodule.c
@@ -1552,6 +1552,13 @@ _Py_Sigset_Converter(PyObject *obj, void *addr)
     Py_DECREF(iterator);
     return 0;
 }
+#else
+int
+_Py_Sigset_Converter(PyObject *obj, void *addr)
+{
+    PyErr_SetFromErrno(PyExc_OSError);
+    return 0;
+}
 #endif /* HAVE_SIGSET_T */
 
 #ifdef MS_WINDOWS
-- 
2.25.1


From 88529d19154fae757a58229e76c0fb849d279725 Mon Sep 17 00:00:00 2001
From: Roman Yurchak <rth.yurchak@gmail.com>
Date: Mon, 28 Feb 2022 00:53:53 -0500
Subject: [PATCH 03/10] fix Py_Sigset_Converter

---
 Modules/posixmodule.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/Modules/posixmodule.c b/Modules/posixmodule.c
index 03de470323..b115552dcd 100644
--- a/Modules/posixmodule.c
+++ b/Modules/posixmodule.c
@@ -1552,6 +1552,13 @@ _Py_Sigset_Converter(PyObject *obj, void *addr)
     Py_DECREF(iterator);
     return 0;
 }
+#else
+int
+_Py_Sigset_Converter(PyObject *obj, void *addr)
+{
+    PyErr_SetFromErrno(PyExc_OSError);
+    return 0;
+}
 #endif /* HAVE_SIGSET_T */
 
 #ifdef MS_WINDOWS
-- 
2.25.1

