libyamlcpp: Disable build & install of Google Test
libyamlcpp: Disable build & install of Google Test

The source repo includes a copy of Google Test, which is build
and installed by default, which may lead to the wrong Google Test
being used by packages using yaml-cpp.

NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs