Stop intercepting some malloc-related functions on FreeBSD and macOS

Summary:
In https://bugs.freebsd.org/215125 I was notified that some configure
scripts attempt to test for the Linux-specific `mallinfo` and `mallopt`
functions by compiling and linking small programs which references the
functions, and observing whether that results in errors.

FreeBSD and macOS do not have the `mallinfo` and `mallopt` functions, so
normally these tests would fail, but when sanitizers are enabled, they
incorrectly succeed, because the sanitizers define interceptors for
these functions.  This also applies to some other malloc-related
functions, such as `memalign`, `pvalloc` and `cfree`.

Fix this by not intercepting `mallinfo`, `mallopt`, `memalign`,
`pvalloc` and `cfree` for FreeBSD and macOS, in all sanitizers.

Reviewers: emaste, kcc

Subscribers: hans, joerg, llvm-commits, kubamracek

Differential Revision: https://reviews.llvm.org/D27654

llvm-svn: 293337