[Sanitizer] Intercept arc4random_buf / arc4random_addrandom on FreeBSD/NetBSD

- Disabled on purpose on Android and Darwin platform (for now).
- Darwin supports it, would need interception in its specific code before enabling it.
- Linux does not support it but only via third party library.
- Android supports it via bionic however it is known to have issue with older versions of the implementations. Can be enabled by an Android committer later on if necessary once there is more 'certainity'/been more tested.

Reviewers: krytarowski, vitalybuka

Reviewed By: krytarowski

Differential Revision: https://reviews.llvm.org/D56125

llvm-svn: 350123