test: add ability to skip common flag checks

Currently, `common/index.js` checks that our test files are
spawned with the flags specified in `// Flags:`, and re-spawns
with them if they are not found.

This can be *very* annoying, for example when debugging using
debuggers that attach to the parent process, or when intentionally
testing with flags that are different from the specified ones.

This adds a `NODE_SKIP_FLAG_CHECK` environment variable check.
Setting it to a non-empty value will skip the flag checks altogether.

PR-URL: #27254
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Beth Griggs <Bethany.Griggs@uk.ibm.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Yuta Hiroto <hello@hiroppy.me>
Reviewed-By: Anto Aravinth <anto.aravinth.cse@gmail.com>

test/common/index.js

@@ -51,6 +51,7 @@ const hasCrypto = Boolean(process.versions.openssl);
 // If the binary was built without-ssl then the crypto flags are
 // invalid (bad option). The test itself should handle this case.
 if (process.argv.length === 2 &&
+    !process.env.NODE_SKIP_FLAG_CHECK &&
     isMainThread &&
     hasCrypto &&
     module.parent &&
@@ -82,7 +83,8 @@ if (process.argv.length === 2 &&
           (process.features.inspector || !flag.startsWith('--inspect'))) {
         console.log(
           'NOTE: The test started as a child_process using these flags:',
-          util.inspect(flags)
+          util.inspect(flags),
+          'Use NODE_SKIP_FLAG_CHECK to run the test with the original flags.'
         );
         const args = [...flags, ...process.execArgv, ...process.argv.slice(1)];
         const options = { encoding: 'utf8', stdio: 'inherit' };