dont include objc when INCLUDE_OBJC not set

[holymonson]

We don't need objc for pure CoreFoundation. I check the blame history it seems this logic is what you want.

[YOCKOW]

#3110 seems opposite to this.
@holymonson Do you have any thoughts?

[holymonson]

#3110 seems opposite to this.

Not accurately. #3110 wants not implicitly include objc on win32, while this PR make not implicitly include objc on all platform. I think this one should be merged because it solves #3110 too.

[YOCKOW]

#3110 seems opposite to this.

Not accurately. #3110 wants not implicitly include objc on win32, while this PR make not implicitly include objc on all platform. I think this one should be merged because it solves #3110 too.

Thank you for your response. That's fair enough.
Now I should request proper persons for review...

[YOCKOW]

@swift-ci Please test

[compnerd]

I think that I would like @millenomi or @parkera to chime in on this - I suspect that this impacts more than just the OSS builds.

[parkera]

Closing older PRs after re-core of swift-corelibs-foundation on swift-foundation (#5001).