Fix build-many-glibcs.py style issues.

	* scripts/build-many-glibcs.py (os.path): Do not import.
	(Context): Inherit explicitly from object.  Remove blank line
	between class and docstring.
	(Config): Likewise.
	(Glibc): Likewise.
	(Command): Likewise.
	(CommandList): Likewise.
	(Context.write_files): Store chmod mode in a variable.