CMake iOS build for Firebird 3

Egor Pugin announced on Firebird-Devel list :

With new CMake 3.2.1 it is possible to successfully build Firebird for
iOS platform using CMake.
Updated instructions for iOS build available at
https://bitbucket.org/egor_pugin/firebird_cmake/wiki/Home

The last issue you encounter during building is duplicate symbol error
from clang. It is related to class DatabaseDirectoryList in anonymous
namespace. This class exists in files: src/jrd/jrd.cpp and
src/common/db_alias.cpp.
For my tests I added last underscore symbol to one of those classes
and the build completes.