Improved cmake configs for Windows and Linux.

Now the configs follows the standard cmake-package code: see https://cmake.org/cmake/help/v3.12/manual/cmake-packages.7.html

Downstreamer no longer have to manually specify target_include_directories with ${ASSIMP_INCLUDE_DIRS}, target_link_libraries with ${ASSIMP_LIBRARY_DIRS} and so on.

Downstreamer can now use:
find_package(assimp CONFIG REQUIRED)
target_link_libraries(AWESOME_APP PUBLIC assimp::assimp)
and everything should work.

Added assimpTargets.cmake.in
Added assimpTargets-debug.cmake.in
Added assimpTargets-release.cmake.in
Modified CMakeLists.txt
Modified code/CMakeLists.txt - added ALIAS assimp::assimp

Tested on Ubuntu 18.04 and Windows 10

code/CMakeLists.txt

@@ -910,6 +910,7 @@ IF (ASSIMP_BUILD_NONFREE_C4D_IMPORTER)
 ENDIF (ASSIMP_BUILD_NONFREE_C4D_IMPORTER)
 
 ADD_LIBRARY( assimp ${assimp_src} )
+ADD_LIBRARY(assimp::asimp ALIAS assimp)
 
 TARGET_INCLUDE_DIRECTORIES ( assimp PUBLIC
   $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/../include>