+ operator on a depset is forbidden

[plu]

Error:

ERROR: /Users/joplunien/Development/ios-client/Frameworks/CommonKit/BUILD:24:1: in @tulsi//:tulsi/tulsi_aspects.bzl%tulsi_sources_aspect aspect on apple_binary rule //Frameworks/CommonKit:Example.__internal__.apple_binary: Traceback (most recent call last):
	File "/Users/joplunien/Development/ios-client/Frameworks/CommonKit/BUILD", line 24
		@tulsi//:tulsi/tulsi_aspects.bzl%tulsi_sources_aspect(...)
	File "/private/var/tmp/_bazel_joplunien/9b08c932c25e33662665cc86ff7bb7b1/external/tulsi/tulsi/tulsi_aspects.bzl", line 815, in _tulsi_sources_aspect
		objc_provider.include + objc_provider.iquote
`+` operator on a depset is forbidden. See https://docs.bazel.build/versions/master/skylark/depsets.html for recommendations. Use --incompatible_depset_union=false to temporarily disable this check.
ERROR: Analysis of aspect '@tulsi//:tulsi/tulsi_aspects.bzl%tulsi_sources_aspect of //Frameworks/CommonKit:Example' failed; build aborted: Analysis of target '//Frameworks/CommonKit:Example.__internal__.apple_binary' failed; build aborted
General failure: Bazel aspects could not be built.

https://github.com/bazelbuild/tulsi/blob/master/src/TulsiGenerator/Bazel/tulsi/tulsi_aspects.bzl#L815

Probably needs to be changed similar to bazelbuild/bazel#5817