Fixed cmake error: No known features for C compiler when using the assimp library from another project.

code/CMakeLists.txt

@@ -1172,7 +1172,7 @@ ELSE()
 ENDIF()
 
 # adds C_FLAGS required to compile zip.c on old GCC 4.x compiler
-TARGET_COMPILE_FEATURES(assimp PUBLIC c_std_99)
+TARGET_COMPILE_FEATURES(assimp PRIVATE c_std_99)
 
 TARGET_INCLUDE_DIRECTORIES ( assimp PUBLIC
   $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/../include>