Compute hashes of executable files when migrating

The 'hash' column was added in commit bc1608f (Add hash to
executable files and immutable executables., 2021-03-30), but the
hashes were not computed for existing files, which breaks migrations
from < 8.0.0 (judging fails with error message "Fetching executable
failed for compile script '<n>': Unexpected hash ...").

This commit adds the code to an existing migration
(Version20230508163415, added in DOMjudge 8.3.0) because the code in
that migration uses the file hashes and won't work if they haven't
been computed.

Users who already performed an upgrade from 7.x to 8.3.0 will need to
manually re-run that migration:

    bin/console doctrine:migrations:execute 'DoctrineMigrations\Version20230508163415' --down
    bin/console doctrine:migrations:execute 'DoctrineMigrations\Version20230508163415' --up

webapp/migrations/Version20230508163415.php

@@ -15,11 +15,18 @@ final class Version20230508163415 extends AbstractMigration
 {
     public function getDescription(): string
     {
-        return 'Update hashes of immutable executables';
+        return 'Update hashes of executable files and immutable executables';
     }
 
     public function up(Schema $schema): void
     {
+        $executableFiles = $this->connection->fetchAllAssociative('SELECT execfileid, file_content FROM executable_file');
+        foreach ($executableFiles as $file) {
+            $this->connection->executeStatement('UPDATE executable_file SET hash = :hash WHERE execfileid = :id', [
+                'hash' => md5($file['file_content']),
+                'id' => $file['execfileid']
+            ]);
+        }
         $immutableExecutables = $this->connection->fetchAllAssociative('SELECT immutable_execid FROM immutable_executable');
         foreach ($immutableExecutables as $immutableExecutable) {
             $files = $this->connection->fetchAllAssociative('SELECT hash, filename, is_executable FROM executable_file WHERE immutable_execid = :id', ['id' => $immutableExecutable['immutable_execid']]);
@@ -32,7 +39,7 @@ public function up(Schema $schema): void
                     )
                 )
             );
-            $this->connection->executeQuery('UPDATE immutable_executable SET hash = :hash WHERE immutable_execid = :id', [
+            $this->connection->executeStatement('UPDATE immutable_executable SET hash = :hash WHERE immutable_execid = :id', [
                 'hash' => $newHash,
                 'id' => $immutableExecutable['immutable_execid'],
             ]);