概要

[PostProcessBuild]
private static void OnPostProcessBuild
(
    BuildTarget buildTarget,
    string      pathToBuiltProject
)
{
    if ( buildTarget != BuildTarget.iOS ) return;

    var projectPath = PBXProject.GetPBXProjectPath( pathToBuiltProject );
    var project     = new PBXProject();

    project.ReadFromFile( projectPath ); // ★

PBXProject.ReadFromFile を呼び忘れていた