Fix zlibstream macOS build
Fix zlibstream macOS build

The definition of strerror_r() on macOS is different. Check __APPLE__ to
fix the build.

btccom/btcpool,btccom/btcpool,btccom/btcpool,btccom/btcpool,btccom/btcpool,btccom/btcpool,btccom/btcpool,btccom/btcpool