patch 8.1.2129: using hard coded executable path in test

Problem:    Using hard coded executable path in test.
Solution:   Use v:progpath. Use $VIMRUNTIME instead of "runtime". (James
            McCoy, closes #5025)
diff --git a/src/testdir/test_compiler.vim b/src/testdir/test_compiler.vim
index 40d3cdb..06522d7 100644
--- a/src/testdir/test_compiler.vim
+++ b/src/testdir/test_compiler.vim
@@ -39,9 +39,9 @@
 
 func Test_compiler_without_arg()
   let a=split(execute('compiler'))
-  call assert_match('^.*runtime/compiler/ant.vim$',   a[0])
-  call assert_match('^.*runtime/compiler/bcc.vim$',   a[1])
-  call assert_match('^.*runtime/compiler/xmlwf.vim$', a[-1])
+  call assert_match($VIMRUNTIME .. '/compiler/ant.vim$',   a[0])
+  call assert_match($VIMRUNTIME .. '/compiler/bcc.vim$',   a[1])
+  call assert_match($VIMRUNTIME .. '/compiler/xmlwf.vim$', a[-1])
 endfunc
 
 func Test_compiler_completion()