lang/swift6: Fix compilation of math functions when using c++ interoperability modeHEADmain

The following code failed to build if it was compiled with c++
interoperability mode:
```
import Foundation
print(log2(2.0))
```
with the following error:
error: reference to declaration 'log2' broken by a context change; the declaration kind of 'log2'  changed since building 'Foundation', it was in 'SwiftGlibc' and now a candidate is found only in 'Foundation'

This commit fixes it.

0 files changed, 0 insertions, 0 deletions