vim-patch:8.1.1461: tests do not run or are not reliable on some systems

Problem:    Tests do not run or are not reliable on some systems.
Solution:   Use "findstr" instead of "grep" on MS-Windows. Clear
            PROMPT_COMMAND in the terminal test. Delete temp file. Wait for
            output after executing a debug command. (Yegappan Lakshmanan,
            closes vim/vim#4479)
ddd3308782

Ignored changes to testdir/test_terminal.vim.

src/nvim/testdir/test_debugger.vim

@@ -52,16 +52,16 @@ func Test_Debugger()
   let buf = RunVimInTerminal('-S Xtest.vim', {})
 
   " Start the Vim debugger
-  call RunDbgCmd(buf, ':debug echo Foo()')
+  call RunDbgCmd(buf, ':debug echo Foo()', ['cmd: echo Foo()'])
 
   " Create a few stack frames by stepping through functions
-  call RunDbgCmd(buf, 'step')
-  call RunDbgCmd(buf, 'step')
-  call RunDbgCmd(buf, 'step')
-  call RunDbgCmd(buf, 'step')
-  call RunDbgCmd(buf, 'step')
-  call RunDbgCmd(buf, 'step')
-  call RunDbgCmd(buf, 'step')
+  call RunDbgCmd(buf, 'step', ['line 1: let var1 = 1'])
+  call RunDbgCmd(buf, 'step', ['line 2: let var2 = Bar(var1) + 9'])
+  call RunDbgCmd(buf, 'step', ['line 1: let var1 = 2 + a:var'])
+  call RunDbgCmd(buf, 'step', ['line 2: let var2 = Bazz(var1) + 4'])
+  call RunDbgCmd(buf, 'step', ['line 1: try'])
+  call RunDbgCmd(buf, 'step', ['line 2: let var1 = 3 + a:var'])
+  call RunDbgCmd(buf, 'step', ['line 3: let var3 = "another var"'])
 
   " check backtrace
   call RunDbgCmd(buf, 'backtrace', [

src/nvim/testdir/test_environ.vim

@@ -36,7 +36,7 @@ func Test_external_env()
 
   call setenv('FOO', v:null)
   if has('win32')
-    let result = system('set | grep ^FOO=')
+    let result = system('set | findstr ^FOO=')
   else
     let result = system('env | grep ^FOO=')
   endif

src/nvim/testdir/test_filetype.vim

@@ -522,7 +522,11 @@ func CheckItems(checks)
       catch
 	call assert_report('cannot edit "' . names[i] . '": ' . v:exception)
       endtry
-      call assert_equal(ft, &filetype, 'with file name: ' . names[i])
+      if &filetype == '' && &readonly
+	" File exists but not able to edit it (permission denied)
+      else
+	call assert_equal(ft, &filetype, 'with file name: ' . names[i])
+      endif
       bwipe!
     endfor
   endfor

src/nvim/testdir/test_source.vim

@@ -44,4 +44,5 @@ func Test_source_sandbox()
   call assert_equal('hello', getline(1))
   call assert_fails('sandbox source! Xsourcehello', 'E48:')
   bwipe!
+  call delete('Xsourcehello')
 endfunc