fix(process): avoid unexpected behavior when PTY chdir failed (#37614)

Problem:  Unexpected behavior after PTY child process fails to chdir(),
          as it then thinks it's the parent process.
Solution: Exit the child process instead of returning.

src/nvim/os/pty_proc_unix.c

@@ -263,7 +263,7 @@ void pty_proc_teardown(Loop *loop)
 }
 
 static void init_child(PtyProc *ptyproc)
-  FUNC_ATTR_NONNULL_ALL
+  FUNC_ATTR_NONNULL_ALL FUNC_ATTR_NORETURN
 {
 #if defined(HAVE__NSGETENVIRON)
 # define environ (*_NSGetEnviron())
@@ -285,7 +285,7 @@ static void init_child(PtyProc *ptyproc)
   // Don't use os_chdir() as that may buffer UI events unnecessarily.
   if (proc->cwd && (err = uv_chdir(proc->cwd)) != 0) {
     ELOG("chdir(%s) failed: %s", proc->cwd, uv_strerror(err));
-    return;
+    _exit(122);
   }
 
   const char *prog = proc_get_exepath(proc);

test/functional/core/job_spec.lua

@@ -297,18 +297,42 @@ describe('jobs', function()
   end)
 
   it('error on non-executable `cwd`', function()
-    if is_os('win') then
-      return -- Not applicable for Windows.
-    end
+    skip(is_os('win'), 'N/A for Windows')
 
     local dir = 'Xtest_not_executable_dir'
     mkdir(dir)
+    finally(function()
+      rmdir(dir)
+    end)
     fn.setfperm(dir, 'rw-------')
+
     matches(
       '^Vim%(call%):E903: Process failed to start: permission denied: .*',
-      pcall_err(command, "call jobstart(['pwd'], {'cwd': '" .. dir .. "'})")
+      pcall_err(command, ("call jobstart(['pwd'], {'cwd': '%s'})"):format(dir))
     )
-    rmdir(dir)
+  end)
+
+  it('error log and exit status 122 on non-executable `cwd`', function()
+    skip(is_os('win'), 'N/A for Windows')
+
+    local logfile = 'Xchdir_fail_log'
+    clear({ env = { NVIM_LOG_FILE = logfile } })
+
+    local dir = 'Xtest_not_executable_dir'
+    mkdir(dir)
+    finally(function()
+      rmdir(dir)
+      n.check_close()
+      os.remove(logfile)
+    end)
+    fn.setfperm(dir, 'rw-------')
+
+    n.exec(([[
+      let s:chan = jobstart(['pwd'], {'cwd': '%s', 'pty': v:true})
+      let g:status = jobwait([s:chan], 1000)[0]
+    ]]):format(dir))
+    eq(122, eval('g:status'))
+    t.assert_log(('chdir%%(%s%%) failed: permission denied'):format(dir), logfile, 100)
   end)
 
   it('returns 0 when it fails to start', function()