commit 0d4db446982fca7e1b3d9a87b5352e2ffae31deb
author Václav Kubernát <kubervac@fit.cvut.cz> Wed Jul 18 17:18:43 2018 +0200
committer Václav Kubernát <kubervac@fit.cvut.cz> Thu Aug 09 17:28:51 2018 +0200
tree 909de0edb2e661ffc2dfe8928d27b943c8f6a9b4
parent 578347c2cf0cae4844317cd1e8dd92d4ffcbd11f

Implement YangSchema subclass

While we do not necessarily want to use `-isystem` for libyang, we
definitely need to use it for Boost itself. We are only using SPirit X3
directly, but that one still brings in a great deal of other supporting
libraries, including variant and a metaprogramming library.

In our CI environment, these are installed into the same prefix. Boost
itself is OK as we're including it via cmake imported target which uses
-isystem behind the scene. However, if we then add libyang via a regular
target_include_directories, the same path gets pushed into the include
paths, this time without -isystem, but rather as a regular -I. This in
turn starts affecting Boost, and we're screwed.

Fix this by ensuring that we consider libyang to be a system library,
too. We won't get annoyed by some extra warnings and therefore we won't
be able to improve that library as much as the CI would force us
otherwise :).

Change-Id: I7ec9b28501a46f8b2219f4920cbf5c1e4df59d7e