patch 9.0.2045: tests: checking for swap files takes time

Problem:  tests: checking for swap files takes time
Solution: don't check for swap files  when test has been skipped

Check for swap files takes a considerable about of time, so don't do
that for skipped tests to avoid wasting time.

closes: #13371

Signed-off-by: Christian Brabandt <cb@256bit.org>
Co-authored-by: zeertzjq <zeertzjq@outlook.com>
diff --git a/src/testdir/runtest.vim b/src/testdir/runtest.vim
index 0d79bef..d5765d1 100644
--- a/src/testdir/runtest.vim
+++ b/src/testdir/runtest.vim
@@ -277,6 +277,8 @@
     endtry
   endif
 
+  let skipped = v:false
+
   au VimLeavePre * call EarlyExit(g:testfunc)
   if a:test =~ 'Test_nocatch_'
     " Function handles errors itself.  This avoids skipping commands after the
@@ -286,6 +288,7 @@
     if g:skipped_reason != ''
       call add(s:messages, '    Skipped')
       call add(s:skipped, 'SKIPPED ' . a:test . ': ' . g:skipped_reason)
+      let skipped = v:true
     endif
   else
     try
@@ -293,6 +296,7 @@
     catch /^\cskipped/
       call add(s:messages, '    Skipped')
       call add(s:skipped, 'SKIPPED ' . a:test . ': ' . substitute(v:exception, '^\S*\s\+', '',  ''))
+      let skipped = v:true
     catch
       call add(v:errors, 'Caught exception in ' . a:test . ': ' . v:exception . ' @ ' . v:throwpoint)
     endtry
@@ -400,14 +404,16 @@
     endif
   endwhile
 
-  " Check if the test has left any swap files behind.  Delete them before
-  " running tests again, they might interfere.
-  let swapfiles = s:GetSwapFileList()
-  if len(swapfiles) > 0
-    call add(s:messages, "Found swap files: " .. string(swapfiles))
-    for name in swapfiles
-      call delete(name)
-    endfor
+  if !skipped
+    " Check if the test has left any swap files behind.  Delete them before
+    " running tests again, they might interfere.
+    let swapfiles = s:GetSwapFileList()
+    if len(swapfiles) > 0
+      call add(s:messages, "Found swap files: " .. string(swapfiles))
+      for name in swapfiles
+        call delete(name)
+      endfor
+    endif
   endif
 endfunc