Append '-SOVERSION' to DLL base file name for mingw builds to match common style

code/CMakeLists.txt

@@ -1261,6 +1261,12 @@ SET_TARGET_PROPERTIES( assimp PROPERTIES
   OUTPUT_NAME assimp${LIBRARY_SUFFIX}
 )
 
+if (WIN32 AND CMAKE_COMPILER_IS_GNUCXX AND BUILD_SHARED_LIBS)
+  set_target_properties(assimp PROPERTIES
+    SUFFIX "-${ASSIMP_SOVERSION}${CMAKE_SHARED_LIBRARY_SUFFIX}"
+  )
+endif()
+
 if (APPLE)
   if (ASSIMP_BUILD_FRAMEWORK)
     SET_TARGET_PROPERTIES( assimp PROPERTIES