Disable getentropy on Mac to support 10.10

According to the headers, getentropy became available in MacOSX 10.12

We still have some builders on Mac 10.10 that are downstream consumers
of this python executable. I don't expect them to live for that much
longer, but in the meantime, disable the getentropy call that's causing
them problems.

Bug: 180443630
Test: run built py3-cmd binary on a 10.10 machine
Change-Id: I0145301d12e497df08bb94a1ffa679efa2d8e6fd
(cherry picked from commit d948d44e8858597a19cae32f1d4443dd60a826eb)
2 files changed