Several distributions usually decide for shared external libraries
instead of an usual embedded, for security reasons, duplicatiion issues.
This change enable the possibility to set SYSTEM_IRRXML=ON for detect
and build against a system installed irrxml.
By default, the internal copy is compiled.
Changes on build:
- Added a FindIrrXML cmake module.
- Moved the source recipe for proper CMakeLists inside contrib directory
- Includes aren't path based anymore, using the provided INCLUDE_DIR
- Compiler option are grouped in a singled entry on main CMakeLists
Note: Current internal assimp irrXML is older than upstream irrlicht 1.8.4.
To enable usage of this version, code need to be patched.
Helio Chissini de Castro