export tinyxml cmake target

[briansoe66]

Rewrite tinyxml_cmakelists.txt to export cmake target.
FindTinyXML.cmake and enforce-use-stl.patch are no longer needed.

Original method to use tinyxml:

list(APPEND CMAKE_MODULE_PATH path-to-FindTinyXML.cmake)
find_package(TinyXML REQUIRED)
target_include_directories(my-target PUBLIC ${TinyXML_INCLUDE_DIRS})
target_link_libraries(my-target PUBLIC ${TinyXML_LIBRARIES})
add_definitions(TIXML_USE_STL)

New method to use tinyxml:

find_package(tinyxml REQUIRED)
target_link_libaries(my-target PUBLIC tinyxml::tinyxml)

NOTE: TinyXML_INCLUDE_DIRS and TinyXML_LIBRARIES are no longer defined. They probably should be defined, for backward compatibility, but I don't know how to do this.

[gbiggs]

CI:

• Linux
• Linux-aarch64
• Windows

[gbiggs]

@briansoe66 Can you please take a look at the CI output and correct the error that's occurring? I get the same error when I build it locally.