pythongh-127627: Add posix._emscripten_debugger function (python#127628)

Add a posix._emscripten_debugger function to add an emscripten breakpoint.

Author: hoodmane

Misc/NEWS.d/next/Library/2024-12-05-10-14-52.gh-issue-127627.fgCHOZ.rst

@@ -0,0 +1,2 @@
+Added ``posix._emscripten_debugger()`` to help with debugging the test suite on
+the Emscripten target.

Modules/clinic/posixmodule.c.h

@@ -84,6 +84,9 @@
    extern char * _getpty(int *, int, mode_t, int);
 #endif
 
+#ifdef __EMSCRIPTEN__
+#include "emscripten.h" // emscripten_debugger()
+#endif
 
 /*
  * A number of APIs are available on macOS from a certain macOS version.
@@ -16845,8 +16848,24 @@ os__create_environ_impl(PyObject *module)
 }
 
 
-static PyMethodDef posix_methods[] = {
+#ifdef __EMSCRIPTEN__
+/*[clinic input]
+os._emscripten_debugger
+
+Create a breakpoint for the JavaScript debugger. Emscripten only.
+[clinic start generated code]*/
+
+static PyObject *
+os__emscripten_debugger_impl(PyObject *module)
+/*[clinic end generated code: output=ad47dc3bf0661343 input=d814b1877fb6083a]*/
+{
+    emscripten_debugger();
+    Py_RETURN_NONE;
+}
+#endif /* __EMSCRIPTEN__ */
+
 
+static PyMethodDef posix_methods[] = {
     OS_STAT_METHODDEF
     OS_ACCESS_METHODDEF
     OS_TTYNAME_METHODDEF
@@ -17060,6 +17079,7 @@ static PyMethodDef posix_methods[] = {
     OS__INPUTHOOK_METHODDEF
     OS__IS_INPUTHOOK_INSTALLED_METHODDEF
     OS__CREATE_ENVIRON_METHODDEF
+    OS__EMSCRIPTEN_DEBUGGER_METHODDEF
     {NULL,              NULL}            /* Sentinel */
 };