[6.0] Import new Android overlay or Bionic module #1660
                
     Merged
            
            
          
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Explanation: Now that this new overlay was merged into the 6.0 compiler too in swiftlang/swift#74758, this adds the overlay to the six files that currently
import Glibcin this repo and fixes a build error becausestrsignal()always returns_Nonnullin the latest Android NDK 26.Scope: Add imports and a build fix on Android only
Issue: None
Original PR: #1647
Risk: None
Testing: Passed all CI on trunk, plus now builds with the new Android overlay on my daily Android CI, finagolfin/swift-android-sdk#156
Reviewer: @compnerd
@artemcm, easy review.