hooks: Add "sqlalchemy.ext.baked" to sqlalchemy hook.

For issue #5106, added "sqlalchemy.ext.baked" to the hidden imports
list of sqlalchemy hook file hook-sqlalchemy.py. This is because it was
missing.

PyInstaller/hooks/hook-sqlalchemy.py

@@ -24,6 +24,10 @@
 # are not. We should explicitly include database backends.
 hiddenimports = ['pysqlite2', 'MySQLdb', 'psycopg2']
 
+# add sqlalchemy.ext.baked to hidden imports
+baked = exec_statement('from sqlalchemy.ext import baked')
+hiddenimports.append(baked)
+
 # In SQLAlchemy >= 0.6, the "sqlalchemy.dialects" package provides dialects.
 if is_module_satisfies('sqlalchemy >= 0.6'):
     dialects = exec_statement("import sqlalchemy.dialects;print(sqlalchemy.dialects.__all__)")