[cmake] find TinyXML-2 without CMake config files

[Rechi]

TinyXML-2 can be built with meson, which doesn't generate the CMake config files.

fixes #337

[garbear]

Nice, thanks for adding this file!

[Copilot]

Pull Request Overview

This PR adds a CMake find module for the TinyXML2 library to enable the project to locate and link against TinyXML2 in various installation scenarios (system-wide CONFIG-based installation, pkg-config, or manual paths).

• Adds fallback mechanisms for finding TinyXML2 using CONFIG mode, pkg-config, and manual path search
• Creates an imported target tinyxml2::tinyxml2 for modern CMake usage

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[Copilot]

The documentation header is incomplete compared to other find modules in the project (FindUDEV.cmake and FindSdl2.cmake). It should follow the .rst: format and document the exported variables and imported targets. Add documentation listing TINYXML2_FOUND, TINYXML2_INCLUDE_DIR, TINYXML2_LIBRARY, TINYXML2_VERSION, and the tinyxml2::tinyxml2 imported target.

Suggested change

	# FindTinyXML2
	# -----------
	# Finds the TinyXML2 library
	#
	#.rst:
	# FindTinyXML2
	# -----------
	#
	# Find the TinyXML2 library.
	#
	# Imported Targets
	# ^^^^^^^^^^^^^^^
	# tinyxml2::tinyxml2
	# The TinyXML2 library target, if found.
	#
	# Result Variables
	# ^^^^^^^^^^^^^^^
	# TINYXML2_FOUND
	# True if the library was found.
	# TINYXML2_INCLUDE_DIR
	# The directory containing tinyxml2.h.
	# TINYXML2_LIBRARY
	# The path to the TinyXML2 library.
	# TINYXML2_VERSION
	# The version of TinyXML2 found, if available.
	#
	# This module will define the imported target tinyxml2::tinyxml2 if found.
	#
	#.rst:

[garbear]

Wanna grab this AI spew? It doesn't hurt and is kinda nice to have the summary.

[Rechi]

Will pick some parts from FindUDEV.cmake. I haven't looked at the file before.

[Copilot]

Using an INTERFACE library with an ALIAS creates a non-relocatable target. This pattern differs from FindUDEV.cmake which uses UNKNOWN IMPORTED library type with set_target_properties. Consider using add_library(tinyxml2::tinyxml2 UNKNOWN IMPORTED) and set_target_properties() to set IMPORTED_LOCATION and INTERFACE_INCLUDE_DIRECTORIES, or guard the target creation with if(NOT TARGET tinyxml2::tinyxml2) to avoid conflicts with CONFIG mode.

Suggested change

	add_library(tinyxml2 INTERFACE)
	target_include_directories(tinyxml2 SYSTEM INTERFACE ${TINYXML2_INCLUDE_DIR})
	target_link_libraries(tinyxml2 INTERFACE ${TINYXML2_LIBRARY})
	add_library(tinyxml2::tinyxml2 ALIAS tinyxml2)
	add_library(tinyxml2::tinyxml2 UNKNOWN IMPORTED)
	set_target_properties(tinyxml2::tinyxml2 PROPERTIES
	IMPORTED_LOCATION "${TINYXML2_LIBRARY}"
	INTERFACE_INCLUDE_DIRECTORIES "${TINYXML2_INCLUDE_DIR}"
	)

[garbear]

Should this be updated?