prepare for universal build and CMake 4

[rjsatpdftron]

To work propper with CMake4 the cmake_minimum_required should be at least 3.10.

PDFNetRuby/CMakeLists.txt adjusted to create universal (arm64;x86_64) binaries.

[Copilot]

Pull Request Overview

This PR updates CMake configuration files to prepare for CMake 4 compatibility and enable universal binary builds. The changes standardize the minimum CMake version requirement and simplify macOS architecture targeting.

• Updates minimum CMake version from 2.8.12 to 3.10 across all CMakeLists.txt files
• Replaces conditional ARM64 build logic with universal architecture setting for macOS
• Removes complex conditional CMake version checking in the root CMakeLists.txt

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
PDFTronGo/CMakeLists.txt	Updates minimum CMake version to 3.10
PDFNetRuby/CMakeLists.txt	Updates CMake version and replaces ARM64-specific build flags with universal architecture setting
PDFNetPHP/CMakeLists.txt	Updates minimum CMake version to 3.10
CMakeLists.txt	Simplifies CMake version requirement by removing conditional logic