Python extension build is broken if gflags-dev is installed

In my environment mesos build from master results in broken python api module _mesos.so:

nekto0n@ya-darkstar ~/workspace/mesos/src/python $ PYTHONPATH=build/lib.linux-x86_64-2.7/ python -c "import _mesos"
Traceback (most recent call last):
  File "<string>", line 1, in <module>
ImportError: /home/nekto0n/workspace/mesos/src/python/build/lib.linux-x86_64-2.7/_mesos.so: undefined symbol: _ZN6google14FlagRegistererC1EPKcS2_S2_S2_PvS3_

Unmangled version of symbol looks like this:

google::FlagRegisterer::FlagRegisterer(char const*, char const*, char const*, char const*, void*, void*)

During ./configure step glog finds gflags development files and starts using them, thus implicitly adding dependency on libgflags.so. This breaks Python extensions module and perhaps can break other mesos subsystems when moved to hosts without gflags installed.

This task is done when the ExamplesTest.PythonFramework test will pass on a system with gflags installed.