Allow duplicates within TARGETS_TO_EXPORT

Author: Martchus

cmake/modules/LibraryTarget.cmake

@@ -551,6 +551,7 @@ if (NOT META_NO_INSTALL_TARGETS AND ENABLE_INSTALL_TARGETS)
     if (NOT META_HEADER_ONLY_LIB AND NOT META_PLUGIN_CATEGORY)
         list(APPEND TARGETS_TO_EXPORT "${META_TARGET_NAME}-headers")
     endif ()
+    list(REMOVE_DUPLICATES TARGETS_TO_EXPORT)
     install(
         TARGETS ${TARGETS_TO_EXPORT}
         EXPORT "${NAMESPACE_PREFIX}${META_PROJECT_NAME}${META_CONFIG_SUFFIX}Targets"