Let debugger handle process spawn errors on w32 (Bug#33016)

Since child_setup() is called between block_input()...unblock_input(),
when an error is signaled the Lisp debugger is prevented from
starting.  Therefore, let the callers signal the error instead (which
they already do for non-w32 platforms, just the error message needs an
update).
* src/callproc.c (child_setup) [WINDOWSNT]: Don't call
report_file_error here.
(call_process) [WINDOWNT]:
* src/process.c (create_process) [WINDOWSNT]: Call report_file_errno
here instead, after the unblock_input() call, same as for !WINDOWSNT.
* src/lisp.h (CHILD_SETUP_ERROR_DESC): New preprocessor define.  Flip
the containing ifndef DOS_NT branches so that it's ifdef DOS_NT.
* src/eval.c (when_entered_debugger): Remove.
(syms_of_eval) <internal-when-entered-debugger>: Define it as a Lisp
integer variable instead.
(maybe_call_debugger): Update comment.
* test/src/process-tests.el (make-process-w32-debug-spawn-error):
* test/src/callproc-tests.el (call-process-w32-debug-spawn-error): New
tests.

1 files changed, 1 insertions, 1 deletions

diff --git a/src/process.c b/src/process.c
index 6770a5ed884..0c440371628 100644
--- a/src/process.c
+++ b/src/process.c
@@ -2233,7 +2233,7 @@ create_process (Lisp_Object process, char **new_argv, Lisp_Object current_dir)
   unblock_input ();
 
   if (pid < 0)
-    report_file_errno ("Doing vfork", Qnil, vfork_errno);
+    report_file_errno (CHILD_SETUP_ERROR_DESC, Qnil, vfork_errno);
   else
     {
       /* vfork succeeded.  */