Backported upstream patch to make the pkgconfig file more cross compile
friendly. I don't think anything uses this.

Replaced Installev with CMAKE_INSTALL.

Added PKG_BUILD_PARALLEL for faster compilation.

Signed-off-by: Rosen Penev <rosenp@gmail.com>

Add (lib)jsoncpp to repo

Signed-off-by: Daniel Engberg <daniel.engberg.lists@pyret.net>