Respect top-level CMAKE_*_OUTPUT_DIRECTORY variables

CMakeLists.txt

@@ -341,9 +341,24 @@ INCLUDE (FindPkgMacros)
 INCLUDE (PrecompiledHeader)
 
 # Set Assimp project output directory variables.
-SET(ASSIMP_RUNTIME_OUTPUT_DIRECTORY "${CMAKE_CURRENT_BINARY_DIR}/bin" CACHE STRING "Path for runtime output files")
-SET(ASSIMP_LIBRARY_OUTPUT_DIRECTORY "${CMAKE_CURRENT_BINARY_DIR}/bin" CACHE STRING "Path for library output files")
-SET(ASSIMP_ARCHIVE_OUTPUT_DIRECTORY "${CMAKE_CURRENT_BINARY_DIR}/lib" CACHE STRING "Path for archive output files")
+# Will respect top-level CMAKE_*_OUTPUT_DIRECTORY variables if any are set.
+IF(CMAKE_RUNTIME_OUTPUT_DIRECTORY STREQUAL "")
+  SET(ASSIMP_RUNTIME_OUTPUT_DIRECTORY "${CMAKE_CURRENT_BINARY_DIR}/bin" CACHE STRING "Path for runtime output files")
+ELSE()
+  SET(ASSIMP_RUNTIME_OUTPUT_DIRECTORY ${CMAKE_RUNTIME_OUTPUT_DIRECTORY} CACHE STRING "Path for runtime output files")
+ENDIF()
+
+IF(CMAKE_LIBRARY_OUTPUT_DIRECTORY STREQUAL "")
+  SET(ASSIMP_LIBRARY_OUTPUT_DIRECTORY "${CMAKE_CURRENT_BINARY_DIR}/bin" CACHE STRING "Path for library output files")
+ELSE()
+  SET(ASSIMP_LIBRARY_OUTPUT_DIRECTORY ${CMAKE_LIBRARY_OUTPUT_DIRECTORY} CACHE STRING "Path for runtime output files")
+ENDIF()
+
+IF(CMAKE_ARCHIVE_OUTPUT_DIRECTORY STREQUAL "")
+  SET(ASSIMP_ARCHIVE_OUTPUT_DIRECTORY "${CMAKE_CURRENT_BINARY_DIR}/lib" CACHE STRING "Path for library output files")
+ELSE()
+  SET(ASSIMP_ARCHIVE_OUTPUT_DIRECTORY ${CMAKE_ARCHIVE_OUTPUT_DIRECTORY} CACHE STRING "Path for runtime output files")
+ENDIF()
 
 # Macro used to set the output directories of a target to the
 # respective Assimp output directories.