test: stabilize jit.dump() smoke test

A jiggle in tarantool's initialization code can lead to trace numbers
above 9. We can either:

* accept trace numbers above 9 in the test
* or drop traces from the initialization code in the test and assume
  that the new trace will have number 1.

Igor Munkin suggested to stick with the second approach to avoid
dependency on the initialization code.

NO_DOC=test fixup, no user visible changes
NO_CHANGELOG=see NO_DOC

Co-authored-by: Igor Munkin <imun@tarantool.org>
(cherry picked from commit 92794ddc)

test/app-tap/gh-5983-jit-library-smoke-tests.test.lua

@@ -24,11 +24,11 @@ if #arg == 0 then
   local proc = io.popen(cmd)
   local got = proc:read('*all'):gsub('^%s+', ''):gsub('%s+$', '')
   local expected = table.concat({
-      '---- TRACE %d start',
-      '---- TRACE %d IR',
-      '---- TRACE %d mcode',
-      '---- TRACE %d stop',
-      '---- TRACE %d exit',
+      '---- TRACE 1 start',
+      '---- TRACE 1 IR',
+      '---- TRACE 1 mcode',
+      '---- TRACE 1 stop',
+      '---- TRACE 1 exit',
   }, '.+')
 
   test:like(got, expected , 'jit.dump smoke tests')
@@ -40,5 +40,7 @@ end
 require('jit.dump').start('+tbisrmXaT')
 -- Tune JIT engine to make the test faster and more robust.
 jit.opt.start('hotloop=1')
+-- Purge all existing traces generated on Tarantool startup.
+jit.flush()
 -- Record primitive loop.
 for _ = 1, 3 do end