test: detect missing postmortem metadata

This commit updates test-postmortem-metadata to provide a
more useful error message in the scenario where Node is
compiled without postmortem support.

PR-URL: #27828
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Rich Trott <rtrott@gmail.com>

test/v8-updates/test-postmortem-metadata.js

@@ -41,6 +41,9 @@ const symbols = nm.stdout.toString().split('\n').reduce((filtered, line) => {
 
   return filtered;
 }, []);
+
+assert.notStrictEqual(symbols.length, 0, 'No postmortem metadata detected');
+
 const missing = getExpectedSymbols().filter((symbol) => {
   return !symbols.includes(symbol);
 });