Quote shell commands in logs from build-many-glibcs.py.

Quote shell commands in logs from build-many-glibcs.py.

As requested in
<https://sourceware.org/ml/libc-alpha/2016-11/msg00664.html>, this
patch makes the commands recorded in build-many-glibcs.py quote words
so they can be cut-and-pasted back into a shell.  (Note that these
logs are generated by the wrapper script generated to run commands
with logs, hence the needs for quoting logic to be implemented in that
shell script.)

	* scripts/build-many-glibcs.py (Context.write_files): Make wrapper
	script quote words in command output to log suitably for input to
	the shell.