I just installed poco via brew on my mac.

 brew install --c++11 poco

After running a little sample application if gives me

dyld: lazy symbol binding failed: Symbol not found: _clock_gettime
  Referenced from: /usr/local/opt/poco/lib/libPocoFoundation.45.dylib
  Expected in: /usr/lib/libSystem.B.dylib

OS ---------------------------------------------------------------------------
ProductName: Mac OS X
ProductVersion: 10.11.6
BuildVersion: 15G31
Darwin Kernel Version 15.6.0: Thu Jun 23 18:25:34 PDT 2016; root:xnu-3248.60.10~1/RELEASE_X86_64