patch 8.2.3587: compiler test fails with backslash file separator

Problem:    Compiler test fails with backslash file separator.
Solution:   Accept slash and backslash.
diff --git a/src/testdir/test_compiler.vim b/src/testdir/test_compiler.vim
index 09c03f7..781bac6 100644
--- a/src/testdir/test_compiler.vim
+++ b/src/testdir/test_compiler.vim
@@ -22,7 +22,7 @@
   call assert_fails('let g:current_compiler', 'E121:')
 
   let verbose_efm = execute('verbose set efm')
-  call assert_match('Last set from .*/compiler/perl.vim ', verbose_efm)
+  call assert_match('Last set from .*[/\\]compiler[/\\]perl.vim ', verbose_efm)
 
   call setline(1, ['#!/usr/bin/perl -w', 'use strict;', 'my $foo=1'])
   w!