libchromeos-host: build subset, enabling non-Linux hosts

Adjust the libchromeos-host build so that it doesn't include the
components that rely on Linux-specific signalfd() and openat()

For the error number list, don't include Linux-specific errors.

Finally replace setresuid() and setresgid() with setreuid() and
setregid() on non-Linux platforms.

TEST=libchromeos-host builds on Mac,
  dbus-binding-generator builds and runs on a Mac host,
  peerd's build uses dbus-binding-generator on a Mac host.

Change-Id: Ic68a097d9a007c3392fcdb88b48ed8b27563e45a
3 files changed