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 #4479)
diff --git a/src/testdir/test_debugger.vim b/src/testdir/test_debugger.vim
index 8faf7ac..4c3d672 100644
--- a/src/testdir/test_debugger.vim
+++ b/src/testdir/test_debugger.vim
@@ -52,16 +52,16 @@
   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', [