Make build-many-glibcs.py work on python3.2

I used this patch to run the new build script with python3.2, it may be worth
adding this hack if python3.5 is not widespread (might work with older python,
i haven't tested that).

This patch make build-many-glibcs.py work with python 3.2 by
adding fallback implementation to python 3.5 facilities if they
are not present.

Checked building a x86_64-linux-gnu toolchain with python 3.2.

2016-11-22  Szabolcs Nagy  <szabolcs.nagy@arm.com>

	* scripts/build-many-glibcs.py (os.cpu_count): Add compatibility definition.
	(re.fullmatch, subprocess.run): Likewise.